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<h1>grammar.coffee</h1>
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<p>The CoffeeScript parser is generated by <a href="http://github.com/zaach/jison">Jison</a>
from this grammar file. Jison is a bottom-up parser generator, similar in
style to <a href="http://www.gnu.org/software/bison">Bison</a>, implemented in JavaScript.
It can recognize <a href="http://en.wikipedia.org/wiki/LR_grammar">LALR(1), LR(0), SLR(1), and LR(1)</a>
type grammars. To create the Jison parser, we list the pattern to match
on the left-hand side, and the action to take (usually the creation of syntax
tree nodes) on the right. As the parser runs, it
shifts tokens from our token stream, from left to right, and
<a href="http://en.wikipedia.org/wiki/Bottom-up_parsing">attempts to match</a>
the token sequence against the rules below. When a match can be made, it
reduces into the <a href="http://en.wikipedia.org/wiki/Terminal_and_nonterminal_symbols">nonterminal</a>
(the enclosing name at the top), and we proceed from there.</p>
<p>If you run the <code>cake build:parser</code> command, Jison constructs a parse table
from our rules and saves it into <code>lib/parser.js</code>.</p>
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<p>The only dependency is on the <strong>Jison.Parser</strong>.</p>
</div>
<div class="content"><div class='highlight'><pre>{Parser} = <span class="hljs-built_in">require</span> <span class="hljs-string">'jison'</span></pre></div></div>
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<h2 id="jison-dsl">Jison DSL</h2>
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<p>Since we’re going to be wrapped in a function by Jison in any case, if our
action immediately returns a value, we can optimize by removing the function
wrapper and just returning the value directly.</p>
</div>
<div class="content"><div class='highlight'><pre>unwrap = <span class="hljs-regexp">/^function\s*\(\)\s*\{\s*return\s*([\s\S]*);\s*\}/</span></pre></div></div>
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<p>Our handy DSL for Jison grammar generation, thanks to
<a href="http://github.com/creationix">Tim Caswell</a>. For every rule in the grammar,
we pass the pattern-defining string, the action to run, and extra options,
optionally. If no action is specified, we simply pass the value of the
previous nonterminal.</p>
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<div class="content"><div class='highlight'><pre><span class="hljs-function"><span class="hljs-title">o</span> = <span class="hljs-params">(patternString, action, options)</span> -></span>
patternString = patternString.replace <span class="hljs-regexp">/\s{2,}/g</span>, <span class="hljs-string">' '</span>
patternCount = patternString.split(<span class="hljs-string">' '</span>).length
<span class="hljs-keyword">return</span> [patternString, <span class="hljs-string">'$$ = $1;'</span>, options] <span class="hljs-keyword">unless</span> action
action = <span class="hljs-keyword">if</span> match = unwrap.exec action <span class="hljs-keyword">then</span> match[<span class="hljs-number">1</span>] <span class="hljs-keyword">else</span> <span class="hljs-string">"(<span class="hljs-subst">#{action}</span>())"</span></pre></div></div>
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<p>All runtime functions we need are defined on “yy”</p>
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<div class="content"><div class='highlight'><pre> action = action.replace <span class="hljs-regexp">/\bnew /g</span>, <span class="hljs-string">'$&yy.'</span>
action = action.replace <span class="hljs-regexp">/\b(?:Block\.wrap|extend)\b/g</span>, <span class="hljs-string">'yy.$&'</span></pre></div></div>
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<p>Returns a function which adds location data to the first parameter passed
in, and returns the parameter. If the parameter is not a node, it will
just be passed through unaffected.</p>
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<div class="content"><div class='highlight'><pre> <span class="hljs-function"><span class="hljs-title">addLocationDataFn</span> = <span class="hljs-params">(first, last)</span> -></span>
<span class="hljs-keyword">if</span> <span class="hljs-keyword">not</span> last
<span class="hljs-string">"yy.addLocationDataFn(@<span class="hljs-subst">#{first}</span>)"</span>
<span class="hljs-keyword">else</span>
<span class="hljs-string">"yy.addLocationDataFn(@<span class="hljs-subst">#{first}</span>, @<span class="hljs-subst">#{last}</span>)"</span>
action = action.replace <span class="hljs-regexp">/LOC\(([0-9]*)\)/g</span>, addLocationDataFn(<span class="hljs-string">'$1'</span>)
action = action.replace <span class="hljs-regexp">/LOC\(([0-9]*),\s*([0-9]*)\)/g</span>, addLocationDataFn(<span class="hljs-string">'$1'</span>, <span class="hljs-string">'$2'</span>)
[patternString, <span class="hljs-string">"$$ = <span class="hljs-subst">#{addLocationDataFn(<span class="hljs-number">1</span>, patternCount)}</span>(<span class="hljs-subst">#{action}</span>);"</span>, options]</pre></div></div>
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<h2 id="grammatical-rules">Grammatical Rules</h2>
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<p>In all of the rules that follow, you’ll see the name of the nonterminal as
the key to a list of alternative matches. With each match’s action, the
dollar-sign variables are provided by Jison as references to the value of
their numeric position, so in this rule:</p>
<pre><code><span class="hljs-string">"Expression UNLESS Expression"</span>
</code></pre><p><code>$1</code> would be the value of the first <code>Expression</code>, <code>$2</code> would be the token
for the <code>UNLESS</code> terminal, and <code>$3</code> would be the value of the second
<code>Expression</code>.</p>
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<div class="content"><div class='highlight'><pre>grammar =</pre></div></div>
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<p>The <strong>Root</strong> is the top-level node in the syntax tree. Since we parse bottom-up,
all parsing must end here.</p>
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<div class="content"><div class='highlight'><pre> <span class="hljs-attribute">Root</span>: [
o <span class="hljs-string">''</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> Block
o <span class="hljs-string">'Body'</span>
]</pre></div></div>
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<p>Any list of statements and expressions, separated by line breaks or semicolons.</p>
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<div class="content"><div class='highlight'><pre> <span class="hljs-attribute">Body</span>: [
o <span class="hljs-string">'Line'</span>,<span class="hljs-function"> -></span> Block.wrap [$<span class="hljs-number">1</span>]
o <span class="hljs-string">'Body TERMINATOR Line'</span>,<span class="hljs-function"> -></span> $<span class="hljs-number">1.</span>push $<span class="hljs-number">3</span>
o <span class="hljs-string">'Body TERMINATOR'</span>
]</pre></div></div>
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<p>Block and statements, which make up a line in a body.</p>
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<div class="content"><div class='highlight'><pre> <span class="hljs-attribute">Line</span>: [
o <span class="hljs-string">'Expression'</span>
o <span class="hljs-string">'Statement'</span>
]</pre></div></div>
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<p>Pure statements which cannot be expressions.</p>
</div>
<div class="content"><div class='highlight'><pre> <span class="hljs-attribute">Statement</span>: [
o <span class="hljs-string">'Return'</span>
o <span class="hljs-string">'Comment'</span>
o <span class="hljs-string">'STATEMENT'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> Literal $<span class="hljs-number">1</span>
]</pre></div></div>
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<p>All the different types of expressions in our language. The basic unit of
CoffeeScript is the <strong>Expression</strong> — everything that can be an expression
is one. Blocks serve as the building blocks of many other rules, making
them somewhat circular.</p>
</div>
<div class="content"><div class='highlight'><pre> <span class="hljs-attribute">Expression</span>: [
o <span class="hljs-string">'Value'</span>
o <span class="hljs-string">'Invocation'</span>
o <span class="hljs-string">'Code'</span>
o <span class="hljs-string">'Operation'</span>
o <span class="hljs-string">'Assign'</span>
o <span class="hljs-string">'If'</span>
o <span class="hljs-string">'Try'</span>
o <span class="hljs-string">'While'</span>
o <span class="hljs-string">'For'</span>
o <span class="hljs-string">'Switch'</span>
o <span class="hljs-string">'Class'</span>
o <span class="hljs-string">'Throw'</span>
]</pre></div></div>
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<p>An indented block of expressions. Note that the <a href="rewriter.html">Rewriter</a>
will convert some postfix forms into blocks for us, by adjusting the
token stream.</p>
</div>
<div class="content"><div class='highlight'><pre> <span class="hljs-attribute">Block</span>: [
o <span class="hljs-string">'INDENT OUTDENT'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> Block
o <span class="hljs-string">'INDENT Body OUTDENT'</span>,<span class="hljs-function"> -></span> $<span class="hljs-number">2</span>
]</pre></div></div>
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<p>A literal identifier, a variable name or property.</p>
</div>
<div class="content"><div class='highlight'><pre> <span class="hljs-attribute">Identifier</span>: [
o <span class="hljs-string">'IDENTIFIER'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> Literal $<span class="hljs-number">1</span>
]</pre></div></div>
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<p>Alphanumerics are separated from the other <strong>Literal</strong> matchers because
they can also serve as keys in object literals.</p>
</div>
<div class="content"><div class='highlight'><pre> <span class="hljs-attribute">AlphaNumeric</span>: [
o <span class="hljs-string">'NUMBER'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> Literal $<span class="hljs-number">1</span>
o <span class="hljs-string">'String'</span>
]
<span class="hljs-attribute">String</span>: [
o <span class="hljs-string">'STRING'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> Literal $<span class="hljs-number">1</span>
o <span class="hljs-string">'STRING_START Body STRING_END'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> Parens $<span class="hljs-number">2</span>
]
<span class="hljs-attribute">Regex</span>: [
o <span class="hljs-string">'REGEX'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> Literal $<span class="hljs-number">1</span>
o <span class="hljs-string">'REGEX_START Invocation REGEX_END'</span>,<span class="hljs-function"> -></span> $<span class="hljs-number">2</span>
]</pre></div></div>
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<p>All of our immediate values. Generally these can be passed straight
through and printed to JavaScript.</p>
</div>
<div class="content"><div class='highlight'><pre> <span class="hljs-attribute">Literal</span>: [
o <span class="hljs-string">'AlphaNumeric'</span>
o <span class="hljs-string">'JS'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> Literal $<span class="hljs-number">1</span>
o <span class="hljs-string">'Regex'</span>
o <span class="hljs-string">'DEBUGGER'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> Literal $<span class="hljs-number">1</span>
o <span class="hljs-string">'UNDEFINED'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> Undefined
o <span class="hljs-string">'NULL'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> Null
o <span class="hljs-string">'BOOL'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> Bool $<span class="hljs-number">1</span>
]</pre></div></div>
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<p>Assignment of a variable, property, or index to a value.</p>
</div>
<div class="content"><div class='highlight'><pre> <span class="hljs-attribute">Assign</span>: [
o <span class="hljs-string">'Assignable = Expression'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> Assign $<span class="hljs-number">1</span>, $<span class="hljs-number">3</span>
o <span class="hljs-string">'Assignable = TERMINATOR Expression'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> Assign $<span class="hljs-number">1</span>, $<span class="hljs-number">4</span>
o <span class="hljs-string">'Assignable = INDENT Expression OUTDENT'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> Assign $<span class="hljs-number">1</span>, $<span class="hljs-number">4</span>
]</pre></div></div>
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<p>Assignment when it happens within an object literal. The difference from
the ordinary <strong>Assign</strong> is that these allow numbers and strings as keys.</p>
</div>
<div class="content"><div class='highlight'><pre> <span class="hljs-attribute">AssignObj</span>: [
o <span class="hljs-string">'ObjAssignable'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> Value $<span class="hljs-number">1</span>
o <span class="hljs-string">'ObjAssignable : Expression'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> Assign LOC(<span class="hljs-number">1</span>)(<span class="hljs-keyword">new</span> Value $<span class="hljs-number">1</span>), $<span class="hljs-number">3</span>, <span class="hljs-string">'object'</span>,
<span class="hljs-attribute">operatorToken</span>: LOC(<span class="hljs-number">2</span>)(<span class="hljs-keyword">new</span> Literal $<span class="hljs-number">2</span>)
o <span class="hljs-string">'ObjAssignable :
INDENT Expression OUTDENT'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> Assign LOC(<span class="hljs-number">1</span>)(<span class="hljs-keyword">new</span> Value $<span class="hljs-number">1</span>), $<span class="hljs-number">4</span>, <span class="hljs-string">'object'</span>,
<span class="hljs-attribute">operatorToken</span>: LOC(<span class="hljs-number">2</span>)(<span class="hljs-keyword">new</span> Literal $<span class="hljs-number">2</span>)
o <span class="hljs-string">'SimpleObjAssignable = Expression'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> Assign LOC(<span class="hljs-number">1</span>)(<span class="hljs-keyword">new</span> Value $<span class="hljs-number">1</span>), $<span class="hljs-number">3</span>, <span class="hljs-literal">null</span>,
<span class="hljs-attribute">operatorToken</span>: LOC(<span class="hljs-number">2</span>)(<span class="hljs-keyword">new</span> Literal $<span class="hljs-number">2</span>)
o <span class="hljs-string">'SimpleObjAssignable =
INDENT Expression OUTDENT'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> Assign LOC(<span class="hljs-number">1</span>)(<span class="hljs-keyword">new</span> Value $<span class="hljs-number">1</span>), $<span class="hljs-number">4</span>, <span class="hljs-literal">null</span>,
<span class="hljs-attribute">operatorToken</span>: LOC(<span class="hljs-number">2</span>)(<span class="hljs-keyword">new</span> Literal $<span class="hljs-number">2</span>)
o <span class="hljs-string">'Comment'</span>
]
<span class="hljs-attribute">SimpleObjAssignable</span>: [
o <span class="hljs-string">'Identifier'</span>
o <span class="hljs-string">'ThisProperty'</span>
]
<span class="hljs-attribute">ObjAssignable</span>: [
o <span class="hljs-string">'SimpleObjAssignable'</span>
o <span class="hljs-string">'AlphaNumeric'</span>
]</pre></div></div>
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<p>A return statement from a function body.</p>
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<div class="content"><div class='highlight'><pre> <span class="hljs-attribute">Return</span>: [
o <span class="hljs-string">'RETURN Expression'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> Return $<span class="hljs-number">2</span>
o <span class="hljs-string">'RETURN'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> Return
]</pre></div></div>
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<p>A block comment.</p>
</div>
<div class="content"><div class='highlight'><pre> <span class="hljs-attribute">Comment</span>: [
o <span class="hljs-string">'HERECOMMENT'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> Comment $<span class="hljs-number">1</span>
]</pre></div></div>
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<p>The <strong>Code</strong> node is the function literal. It’s defined by an indented block
of <strong>Block</strong> preceded by a function arrow, with an optional parameter
list.</p>
</div>
<div class="content"><div class='highlight'><pre> <span class="hljs-attribute">Code</span>: [
o <span class="hljs-string">'PARAM_START ParamList PARAM_END FuncGlyph Block'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> Code $<span class="hljs-number">2</span>, $<span class="hljs-number">5</span>, $<span class="hljs-number">4</span>
o <span class="hljs-string">'FuncGlyph Block'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> Code [], $<span class="hljs-number">2</span>, $<span class="hljs-number">1</span>
]</pre></div></div>
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<p>CoffeeScript has two different symbols for functions. <code>-></code> is for ordinary
functions, and <code>=></code> is for functions bound to the current value of <em>this</em>.</p>
</div>
<div class="content"><div class='highlight'><pre> <span class="hljs-attribute">FuncGlyph</span>: [
o <span class="hljs-string">'->'</span>,<span class="hljs-function"> -></span> <span class="hljs-string">'func'</span>
o <span class="hljs-string">'=>'</span>,<span class="hljs-function"> -></span> <span class="hljs-string">'boundfunc'</span>
]</pre></div></div>
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<p>An optional, trailing comma.</p>
</div>
<div class="content"><div class='highlight'><pre> <span class="hljs-attribute">OptComma</span>: [
o <span class="hljs-string">''</span>
o <span class="hljs-string">','</span>
]</pre></div></div>
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<p>The list of parameters that a function accepts can be of any length.</p>
</div>
<div class="content"><div class='highlight'><pre> <span class="hljs-attribute">ParamList</span>: [
o <span class="hljs-string">''</span>,<span class="hljs-function"> -></span> []
o <span class="hljs-string">'Param'</span>,<span class="hljs-function"> -></span> [$<span class="hljs-number">1</span>]
o <span class="hljs-string">'ParamList , Param'</span>,<span class="hljs-function"> -></span> $<span class="hljs-number">1.</span>concat $<span class="hljs-number">3</span>
o <span class="hljs-string">'ParamList OptComma TERMINATOR Param'</span>,<span class="hljs-function"> -></span> $<span class="hljs-number">1.</span>concat $<span class="hljs-number">4</span>
o <span class="hljs-string">'ParamList OptComma INDENT ParamList OptComma OUTDENT'</span>,<span class="hljs-function"> -></span> $<span class="hljs-number">1.</span>concat $<span class="hljs-number">4</span>
]</pre></div></div>
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<p>A single parameter in a function definition can be ordinary, or a splat
that hoovers up the remaining arguments.</p>
</div>
<div class="content"><div class='highlight'><pre> <span class="hljs-attribute">Param</span>: [
o <span class="hljs-string">'ParamVar'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> Param $<span class="hljs-number">1</span>
o <span class="hljs-string">'ParamVar ...'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> Param $<span class="hljs-number">1</span>, <span class="hljs-literal">null</span>, <span class="hljs-literal">on</span>
o <span class="hljs-string">'ParamVar = Expression'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> Param $<span class="hljs-number">1</span>, $<span class="hljs-number">3</span>
o <span class="hljs-string">'...'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> Expansion
]</pre></div></div>
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<p>Function Parameters</p>
</div>
<div class="content"><div class='highlight'><pre> <span class="hljs-attribute">ParamVar</span>: [
o <span class="hljs-string">'Identifier'</span>
o <span class="hljs-string">'ThisProperty'</span>
o <span class="hljs-string">'Array'</span>
o <span class="hljs-string">'Object'</span>
]</pre></div></div>
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<p>A splat that occurs outside of a parameter list.</p>
</div>
<div class="content"><div class='highlight'><pre> <span class="hljs-attribute">Splat</span>: [
o <span class="hljs-string">'Expression ...'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> Splat $<span class="hljs-number">1</span>
]</pre></div></div>
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<p>Variables and properties that can be assigned to.</p>
</div>
<div class="content"><div class='highlight'><pre> <span class="hljs-attribute">SimpleAssignable</span>: [
o <span class="hljs-string">'Identifier'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> Value $<span class="hljs-number">1</span>
o <span class="hljs-string">'Value Accessor'</span>,<span class="hljs-function"> -></span> $<span class="hljs-number">1.</span>add $<span class="hljs-number">2</span>
o <span class="hljs-string">'Invocation Accessor'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> Value $<span class="hljs-number">1</span>, [].concat $<span class="hljs-number">2</span>
o <span class="hljs-string">'ThisProperty'</span>
]</pre></div></div>
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<p>Everything that can be assigned to.</p>
</div>
<div class="content"><div class='highlight'><pre> <span class="hljs-attribute">Assignable</span>: [
o <span class="hljs-string">'SimpleAssignable'</span>
o <span class="hljs-string">'Array'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> Value $<span class="hljs-number">1</span>
o <span class="hljs-string">'Object'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> Value $<span class="hljs-number">1</span>
]</pre></div></div>
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<p>The types of things that can be treated as values — assigned to, invoked
as functions, indexed into, named as a class, etc.</p>
</div>
<div class="content"><div class='highlight'><pre> <span class="hljs-attribute">Value</span>: [
o <span class="hljs-string">'Assignable'</span>
o <span class="hljs-string">'Literal'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> Value $<span class="hljs-number">1</span>
o <span class="hljs-string">'Parenthetical'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> Value $<span class="hljs-number">1</span>
o <span class="hljs-string">'Range'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> Value $<span class="hljs-number">1</span>
o <span class="hljs-string">'This'</span>
]</pre></div></div>
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<p>The general group of accessors into an object, by property, by prototype
or by array index or slice.</p>
</div>
<div class="content"><div class='highlight'><pre> <span class="hljs-attribute">Accessor</span>: [
o <span class="hljs-string">'. Identifier'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> Access $<span class="hljs-number">2</span>
o <span class="hljs-string">'?. Identifier'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> Access $<span class="hljs-number">2</span>, <span class="hljs-string">'soak'</span>
o <span class="hljs-string">':: Identifier'</span>,<span class="hljs-function"> -></span> [LOC(<span class="hljs-number">1</span>)(<span class="hljs-keyword">new</span> Access <span class="hljs-keyword">new</span> Literal(<span class="hljs-string">'prototype'</span>)), LOC(<span class="hljs-number">2</span>)(<span class="hljs-keyword">new</span> Access $<span class="hljs-number">2</span>)]
o <span class="hljs-string">'?:: Identifier'</span>,<span class="hljs-function"> -></span> [LOC(<span class="hljs-number">1</span>)(<span class="hljs-keyword">new</span> Access <span class="hljs-keyword">new</span> Literal(<span class="hljs-string">'prototype'</span>), <span class="hljs-string">'soak'</span>), LOC(<span class="hljs-number">2</span>)(<span class="hljs-keyword">new</span> Access $<span class="hljs-number">2</span>)]
o <span class="hljs-string">'::'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> Access <span class="hljs-keyword">new</span> Literal <span class="hljs-string">'prototype'</span>
o <span class="hljs-string">'Index'</span>
]</pre></div></div>
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<p>Indexing into an object or array using bracket notation.</p>
</div>
<div class="content"><div class='highlight'><pre> <span class="hljs-attribute">Index</span>: [
o <span class="hljs-string">'INDEX_START IndexValue INDEX_END'</span>,<span class="hljs-function"> -></span> $<span class="hljs-number">2</span>
o <span class="hljs-string">'INDEX_SOAK Index'</span>,<span class="hljs-function"> -></span> extend $<span class="hljs-number">2</span>, soak : <span class="hljs-literal">yes</span>
]
<span class="hljs-attribute">IndexValue</span>: [
o <span class="hljs-string">'Expression'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> Index $<span class="hljs-number">1</span>
o <span class="hljs-string">'Slice'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> Slice $<span class="hljs-number">1</span>
]</pre></div></div>
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<p>In CoffeeScript, an object literal is simply a list of assignments.</p>
</div>
<div class="content"><div class='highlight'><pre> <span class="hljs-attribute">Object</span>: [
o <span class="hljs-string">'{ AssignList OptComma }'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> Obj $<span class="hljs-number">2</span>, $<span class="hljs-number">1.</span>generated
]</pre></div></div>
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<p>Assignment of properties within an object literal can be separated by
comma, as in JavaScript, or simply by newline.</p>
</div>
<div class="content"><div class='highlight'><pre> <span class="hljs-attribute">AssignList</span>: [
o <span class="hljs-string">''</span>,<span class="hljs-function"> -></span> []
o <span class="hljs-string">'AssignObj'</span>,<span class="hljs-function"> -></span> [$<span class="hljs-number">1</span>]
o <span class="hljs-string">'AssignList , AssignObj'</span>,<span class="hljs-function"> -></span> $<span class="hljs-number">1.</span>concat $<span class="hljs-number">3</span>
o <span class="hljs-string">'AssignList OptComma TERMINATOR AssignObj'</span>,<span class="hljs-function"> -></span> $<span class="hljs-number">1.</span>concat $<span class="hljs-number">4</span>
o <span class="hljs-string">'AssignList OptComma INDENT AssignList OptComma OUTDENT'</span>,<span class="hljs-function"> -></span> $<span class="hljs-number">1.</span>concat $<span class="hljs-number">4</span>
]</pre></div></div>
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<p>Class definitions have optional bodies of prototype property assignments,
and optional references to the superclass.</p>
</div>
<div class="content"><div class='highlight'><pre> <span class="hljs-attribute">Class</span>: [
o <span class="hljs-string">'CLASS'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> Class
o <span class="hljs-string">'CLASS Block'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> Class <span class="hljs-literal">null</span>, <span class="hljs-literal">null</span>, $<span class="hljs-number">2</span>
o <span class="hljs-string">'CLASS EXTENDS Expression'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> Class <span class="hljs-literal">null</span>, $<span class="hljs-number">3</span>
o <span class="hljs-string">'CLASS EXTENDS Expression Block'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> Class <span class="hljs-literal">null</span>, $<span class="hljs-number">3</span>, $<span class="hljs-number">4</span>
o <span class="hljs-string">'CLASS SimpleAssignable'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> Class $<span class="hljs-number">2</span>
o <span class="hljs-string">'CLASS SimpleAssignable Block'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> Class $<span class="hljs-number">2</span>, <span class="hljs-literal">null</span>, $<span class="hljs-number">3</span>
o <span class="hljs-string">'CLASS SimpleAssignable EXTENDS Expression'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> Class $<span class="hljs-number">2</span>, $<span class="hljs-number">4</span>
o <span class="hljs-string">'CLASS SimpleAssignable EXTENDS Expression Block'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> Class $<span class="hljs-number">2</span>, $<span class="hljs-number">4</span>, $<span class="hljs-number">5</span>
]</pre></div></div>
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<p>Ordinary function invocation, or a chained series of calls.</p>
</div>
<div class="content"><div class='highlight'><pre> <span class="hljs-attribute">Invocation</span>: [
o <span class="hljs-string">'Value OptFuncExist Arguments'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> Call $<span class="hljs-number">1</span>, $<span class="hljs-number">3</span>, $<span class="hljs-number">2</span>
o <span class="hljs-string">'Invocation OptFuncExist Arguments'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> Call $<span class="hljs-number">1</span>, $<span class="hljs-number">3</span>, $<span class="hljs-number">2</span>
o <span class="hljs-string">'SUPER'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> Call <span class="hljs-string">'super'</span>, [<span class="hljs-keyword">new</span> Splat <span class="hljs-keyword">new</span> Literal <span class="hljs-string">'arguments'</span>]
o <span class="hljs-string">'SUPER Arguments'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> Call <span class="hljs-string">'super'</span>, $<span class="hljs-number">2</span>
]</pre></div></div>
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<p>An optional existence check on a function.</p>
</div>
<div class="content"><div class='highlight'><pre> <span class="hljs-attribute">OptFuncExist</span>: [
o <span class="hljs-string">''</span>,<span class="hljs-function"> -></span> <span class="hljs-literal">no</span>
o <span class="hljs-string">'FUNC_EXIST'</span>,<span class="hljs-function"> -></span> <span class="hljs-literal">yes</span>
]</pre></div></div>
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<p>The list of arguments to a function call.</p>
</div>
<div class="content"><div class='highlight'><pre> <span class="hljs-attribute">Arguments</span>: [
o <span class="hljs-string">'CALL_START CALL_END'</span>,<span class="hljs-function"> -></span> []
o <span class="hljs-string">'CALL_START ArgList OptComma CALL_END'</span>,<span class="hljs-function"> -></span> $<span class="hljs-number">2</span>
]</pre></div></div>
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<p>A reference to the <em>this</em> current object.</p>
</div>
<div class="content"><div class='highlight'><pre> <span class="hljs-attribute">This</span>: [
o <span class="hljs-string">'THIS'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> Value <span class="hljs-keyword">new</span> Literal <span class="hljs-string">'this'</span>
o <span class="hljs-string">'@'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> Value <span class="hljs-keyword">new</span> Literal <span class="hljs-string">'this'</span>
]</pre></div></div>
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<p>A reference to a property on <em>this</em>.</p>
</div>
<div class="content"><div class='highlight'><pre> <span class="hljs-attribute">ThisProperty</span>: [
o <span class="hljs-string">'@ Identifier'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> Value LOC(<span class="hljs-number">1</span>)(<span class="hljs-keyword">new</span> Literal(<span class="hljs-string">'this'</span>)), [LOC(<span class="hljs-number">2</span>)(<span class="hljs-keyword">new</span> Access($<span class="hljs-number">2</span>))], <span class="hljs-string">'this'</span>
]</pre></div></div>
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<p>The array literal.</p>
</div>
<div class="content"><div class='highlight'><pre> <span class="hljs-attribute">Array</span>: [
o <span class="hljs-string">'[ ]'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> Arr []
o <span class="hljs-string">'[ ArgList OptComma ]'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> Arr $<span class="hljs-number">2</span>
]</pre></div></div>
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<p>Inclusive and exclusive range dots.</p>
</div>
<div class="content"><div class='highlight'><pre> <span class="hljs-attribute">RangeDots</span>: [
o <span class="hljs-string">'..'</span>,<span class="hljs-function"> -></span> <span class="hljs-string">'inclusive'</span>
o <span class="hljs-string">'...'</span>,<span class="hljs-function"> -></span> <span class="hljs-string">'exclusive'</span>
]</pre></div></div>
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<p>The CoffeeScript range literal.</p>
</div>
<div class="content"><div class='highlight'><pre> <span class="hljs-attribute">Range</span>: [
o <span class="hljs-string">'[ Expression RangeDots Expression ]'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> Range $<span class="hljs-number">2</span>, $<span class="hljs-number">4</span>, $<span class="hljs-number">3</span>
]</pre></div></div>
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<p>Array slice literals.</p>
</div>
<div class="content"><div class='highlight'><pre> <span class="hljs-attribute">Slice</span>: [
o <span class="hljs-string">'Expression RangeDots Expression'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> Range $<span class="hljs-number">1</span>, $<span class="hljs-number">3</span>, $<span class="hljs-number">2</span>
o <span class="hljs-string">'Expression RangeDots'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> Range $<span class="hljs-number">1</span>, <span class="hljs-literal">null</span>, $<span class="hljs-number">2</span>
o <span class="hljs-string">'RangeDots Expression'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> Range <span class="hljs-literal">null</span>, $<span class="hljs-number">2</span>, $<span class="hljs-number">1</span>
o <span class="hljs-string">'RangeDots'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> Range <span class="hljs-literal">null</span>, <span class="hljs-literal">null</span>, $<span class="hljs-number">1</span>
]</pre></div></div>
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<p>The <strong>ArgList</strong> is both the list of objects passed into a function call,
as well as the contents of an array literal
(i.e. comma-separated expressions). Newlines work as well.</p>
</div>
<div class="content"><div class='highlight'><pre> <span class="hljs-attribute">ArgList</span>: [
o <span class="hljs-string">'Arg'</span>,<span class="hljs-function"> -></span> [$<span class="hljs-number">1</span>]
o <span class="hljs-string">'ArgList , Arg'</span>,<span class="hljs-function"> -></span> $<span class="hljs-number">1.</span>concat $<span class="hljs-number">3</span>
o <span class="hljs-string">'ArgList OptComma TERMINATOR Arg'</span>,<span class="hljs-function"> -></span> $<span class="hljs-number">1.</span>concat $<span class="hljs-number">4</span>
o <span class="hljs-string">'INDENT ArgList OptComma OUTDENT'</span>,<span class="hljs-function"> -></span> $<span class="hljs-number">2</span>
o <span class="hljs-string">'ArgList OptComma INDENT ArgList OptComma OUTDENT'</span>,<span class="hljs-function"> -></span> $<span class="hljs-number">1.</span>concat $<span class="hljs-number">4</span>
]</pre></div></div>
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<p>Valid arguments are Blocks or Splats.</p>
</div>
<div class="content"><div class='highlight'><pre> <span class="hljs-attribute">Arg</span>: [
o <span class="hljs-string">'Expression'</span>
o <span class="hljs-string">'Splat'</span>
o <span class="hljs-string">'...'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> Expansion
]</pre></div></div>
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<p>Just simple, comma-separated, required arguments (no fancy syntax). We need
this to be separate from the <strong>ArgList</strong> for use in <strong>Switch</strong> blocks, where
having the newlines wouldn’t make sense.</p>
</div>
<div class="content"><div class='highlight'><pre> <span class="hljs-attribute">SimpleArgs</span>: [
o <span class="hljs-string">'Expression'</span>
o <span class="hljs-string">'SimpleArgs , Expression'</span>,<span class="hljs-function"> -></span> [].concat $<span class="hljs-number">1</span>, $<span class="hljs-number">3</span>
]</pre></div></div>
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<p>The variants of <em>try/catch/finally</em> exception handling blocks.</p>
</div>
<div class="content"><div class='highlight'><pre> <span class="hljs-attribute">Try</span>: [
o <span class="hljs-string">'TRY Block'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> Try $<span class="hljs-number">2</span>
o <span class="hljs-string">'TRY Block Catch'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> Try $<span class="hljs-number">2</span>, $<span class="hljs-number">3</span>[<span class="hljs-number">0</span>], $<span class="hljs-number">3</span>[<span class="hljs-number">1</span>]
o <span class="hljs-string">'TRY Block FINALLY Block'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> Try $<span class="hljs-number">2</span>, <span class="hljs-literal">null</span>, <span class="hljs-literal">null</span>, $<span class="hljs-number">4</span>
o <span class="hljs-string">'TRY Block Catch FINALLY Block'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> Try $<span class="hljs-number">2</span>, $<span class="hljs-number">3</span>[<span class="hljs-number">0</span>], $<span class="hljs-number">3</span>[<span class="hljs-number">1</span>], $<span class="hljs-number">5</span>
]</pre></div></div>
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<p>A catch clause names its error and runs a block of code.</p>
</div>
<div class="content"><div class='highlight'><pre> <span class="hljs-attribute">Catch</span>: [
o <span class="hljs-string">'CATCH Identifier Block'</span>,<span class="hljs-function"> -></span> [$<span class="hljs-number">2</span>, $<span class="hljs-number">3</span>]
o <span class="hljs-string">'CATCH Object Block'</span>,<span class="hljs-function"> -></span> [LOC(<span class="hljs-number">2</span>)(<span class="hljs-keyword">new</span> Value($<span class="hljs-number">2</span>)), $<span class="hljs-number">3</span>]
o <span class="hljs-string">'CATCH Block'</span>,<span class="hljs-function"> -></span> [<span class="hljs-literal">null</span>, $<span class="hljs-number">2</span>]
]</pre></div></div>
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<p>Throw an exception object.</p>
</div>
<div class="content"><div class='highlight'><pre> <span class="hljs-attribute">Throw</span>: [
o <span class="hljs-string">'THROW Expression'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> Throw $<span class="hljs-number">2</span>
]</pre></div></div>
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<p>Parenthetical expressions. Note that the <strong>Parenthetical</strong> is a <strong>Value</strong>,
not an <strong>Expression</strong>, so if you need to use an expression in a place
where only values are accepted, wrapping it in parentheses will always do
the trick.</p>
</div>
<div class="content"><div class='highlight'><pre> <span class="hljs-attribute">Parenthetical</span>: [
o <span class="hljs-string">'( Body )'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> Parens $<span class="hljs-number">2</span>
o <span class="hljs-string">'( INDENT Body OUTDENT )'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> Parens $<span class="hljs-number">3</span>
]</pre></div></div>
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<p>The condition portion of a while loop.</p>
</div>
<div class="content"><div class='highlight'><pre> <span class="hljs-attribute">WhileSource</span>: [
o <span class="hljs-string">'WHILE Expression'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> While $<span class="hljs-number">2</span>
o <span class="hljs-string">'WHILE Expression WHEN Expression'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> While $<span class="hljs-number">2</span>, <span class="hljs-attribute">guard</span>: $<span class="hljs-number">4</span>
o <span class="hljs-string">'UNTIL Expression'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> While $<span class="hljs-number">2</span>, <span class="hljs-attribute">invert</span>: <span class="hljs-literal">true</span>
o <span class="hljs-string">'UNTIL Expression WHEN Expression'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> While $<span class="hljs-number">2</span>, <span class="hljs-attribute">invert</span>: <span class="hljs-literal">true</span>, <span class="hljs-attribute">guard</span>: $<span class="hljs-number">4</span>
]</pre></div></div>
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<p>The while loop can either be normal, with a block of expressions to execute,
or postfix, with a single expression. There is no do..while.</p>
</div>
<div class="content"><div class='highlight'><pre> <span class="hljs-attribute">While</span>: [
o <span class="hljs-string">'WhileSource Block'</span>,<span class="hljs-function"> -></span> $<span class="hljs-number">1.</span>addBody $<span class="hljs-number">2</span>
o <span class="hljs-string">'Statement WhileSource'</span>,<span class="hljs-function"> -></span> $<span class="hljs-number">2.</span>addBody LOC(<span class="hljs-number">1</span>) Block.wrap([$<span class="hljs-number">1</span>])
o <span class="hljs-string">'Expression WhileSource'</span>,<span class="hljs-function"> -></span> $<span class="hljs-number">2.</span>addBody LOC(<span class="hljs-number">1</span>) Block.wrap([$<span class="hljs-number">1</span>])
o <span class="hljs-string">'Loop'</span>,<span class="hljs-function"> -></span> $<span class="hljs-number">1</span>
]
<span class="hljs-attribute">Loop</span>: [
o <span class="hljs-string">'LOOP Block'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> While(LOC(<span class="hljs-number">1</span>) <span class="hljs-keyword">new</span> Literal <span class="hljs-string">'true'</span>).addBody $<span class="hljs-number">2</span>
o <span class="hljs-string">'LOOP Expression'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> While(LOC(<span class="hljs-number">1</span>) <span class="hljs-keyword">new</span> Literal <span class="hljs-string">'true'</span>).addBody LOC(<span class="hljs-number">2</span>) Block.wrap [$<span class="hljs-number">2</span>]
]</pre></div></div>
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<p>Array, object, and range comprehensions, at the most generic level.
Comprehensions can either be normal, with a block of expressions to execute,
or postfix, with a single expression.</p>
</div>
<div class="content"><div class='highlight'><pre> <span class="hljs-attribute">For</span>: [
o <span class="hljs-string">'Statement ForBody'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> For $<span class="hljs-number">1</span>, $<span class="hljs-number">2</span>
o <span class="hljs-string">'Expression ForBody'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> For $<span class="hljs-number">1</span>, $<span class="hljs-number">2</span>
o <span class="hljs-string">'ForBody Block'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> For $<span class="hljs-number">2</span>, $<span class="hljs-number">1</span>
]
<span class="hljs-attribute">ForBody</span>: [
o <span class="hljs-string">'FOR Range'</span>,<span class="hljs-function"> -></span> <span class="hljs-attribute">source</span>: (LOC(<span class="hljs-number">2</span>) <span class="hljs-keyword">new</span> Value($<span class="hljs-number">2</span>))
o <span class="hljs-string">'FOR Range BY Expression'</span>,<span class="hljs-function"> -></span> <span class="hljs-attribute">source</span>: (LOC(<span class="hljs-number">2</span>) <span class="hljs-keyword">new</span> Value($<span class="hljs-number">2</span>)), <span class="hljs-attribute">step</span>: $<span class="hljs-number">4</span>
o <span class="hljs-string">'ForStart ForSource'</span>,<span class="hljs-function"> -></span> $<span class="hljs-number">2.</span>own = $<span class="hljs-number">1.</span>own; $<span class="hljs-number">2.</span>name = $<span class="hljs-number">1</span>[<span class="hljs-number">0</span>]; $<span class="hljs-number">2.</span>index = $<span class="hljs-number">1</span>[<span class="hljs-number">1</span>]; $<span class="hljs-number">2</span>
]
<span class="hljs-attribute">ForStart</span>: [
o <span class="hljs-string">'FOR ForVariables'</span>,<span class="hljs-function"> -></span> $<span class="hljs-number">2</span>
o <span class="hljs-string">'FOR OWN ForVariables'</span>,<span class="hljs-function"> -></span> $<span class="hljs-number">3.</span>own = <span class="hljs-literal">yes</span>; $<span class="hljs-number">3</span>
]</pre></div></div>
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<p>An array of all accepted values for a variable inside the loop.
This enables support for pattern matching.</p>
</div>
<div class="content"><div class='highlight'><pre> <span class="hljs-attribute">ForValue</span>: [
o <span class="hljs-string">'Identifier'</span>
o <span class="hljs-string">'ThisProperty'</span>
o <span class="hljs-string">'Array'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> Value $<span class="hljs-number">1</span>
o <span class="hljs-string">'Object'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> Value $<span class="hljs-number">1</span>
]</pre></div></div>
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<p>An array or range comprehension has variables for the current element
and (optional) reference to the current index. Or, <em>key, value</em>, in the case
of object comprehensions.</p>
</div>
<div class="content"><div class='highlight'><pre> <span class="hljs-attribute">ForVariables</span>: [
o <span class="hljs-string">'ForValue'</span>,<span class="hljs-function"> -></span> [$<span class="hljs-number">1</span>]
o <span class="hljs-string">'ForValue , ForValue'</span>,<span class="hljs-function"> -></span> [$<span class="hljs-number">1</span>, $<span class="hljs-number">3</span>]
]</pre></div></div>
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<p>The source of a comprehension is an array or object with an optional guard
clause. If it’s an array comprehension, you can also choose to step through
in fixed-size increments.</p>
</div>
<div class="content"><div class='highlight'><pre> <span class="hljs-attribute">ForSource</span>: [
o <span class="hljs-string">'FORIN Expression'</span>,<span class="hljs-function"> -></span> <span class="hljs-attribute">source</span>: $<span class="hljs-number">2</span>
o <span class="hljs-string">'FOROF Expression'</span>,<span class="hljs-function"> -></span> <span class="hljs-attribute">source</span>: $<span class="hljs-number">2</span>, <span class="hljs-attribute">object</span>: <span class="hljs-literal">yes</span>
o <span class="hljs-string">'FORIN Expression WHEN Expression'</span>,<span class="hljs-function"> -></span> <span class="hljs-attribute">source</span>: $<span class="hljs-number">2</span>, <span class="hljs-attribute">guard</span>: $<span class="hljs-number">4</span>
o <span class="hljs-string">'FOROF Expression WHEN Expression'</span>,<span class="hljs-function"> -></span> <span class="hljs-attribute">source</span>: $<span class="hljs-number">2</span>, <span class="hljs-attribute">guard</span>: $<span class="hljs-number">4</span>, <span class="hljs-attribute">object</span>: <span class="hljs-literal">yes</span>
o <span class="hljs-string">'FORIN Expression BY Expression'</span>,<span class="hljs-function"> -></span> <span class="hljs-attribute">source</span>: $<span class="hljs-number">2</span>, <span class="hljs-attribute">step</span>: $<span class="hljs-number">4</span>
o <span class="hljs-string">'FORIN Expression WHEN Expression BY Expression'</span>,<span class="hljs-function"> -></span> <span class="hljs-attribute">source</span>: $<span class="hljs-number">2</span>, <span class="hljs-attribute">guard</span>: $<span class="hljs-number">4</span>, <span class="hljs-attribute">step</span>: $<span class="hljs-number">6</span>
o <span class="hljs-string">'FORIN Expression BY Expression WHEN Expression'</span>,<span class="hljs-function"> -></span> <span class="hljs-attribute">source</span>: $<span class="hljs-number">2</span>, <span class="hljs-attribute">step</span>: $<span class="hljs-number">4</span>, <span class="hljs-attribute">guard</span>: $<span class="hljs-number">6</span>
]
<span class="hljs-attribute">Switch</span>: [
o <span class="hljs-string">'SWITCH Expression INDENT Whens OUTDENT'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> Switch $<span class="hljs-number">2</span>, $<span class="hljs-number">4</span>
o <span class="hljs-string">'SWITCH Expression INDENT Whens ELSE Block OUTDENT'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> Switch $<span class="hljs-number">2</span>, $<span class="hljs-number">4</span>, $<span class="hljs-number">6</span>
o <span class="hljs-string">'SWITCH INDENT Whens OUTDENT'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> Switch <span class="hljs-literal">null</span>, $<span class="hljs-number">3</span>
o <span class="hljs-string">'SWITCH INDENT Whens ELSE Block OUTDENT'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> Switch <span class="hljs-literal">null</span>, $<span class="hljs-number">3</span>, $<span class="hljs-number">5</span>
]
<span class="hljs-attribute">Whens</span>: [
o <span class="hljs-string">'When'</span>
o <span class="hljs-string">'Whens When'</span>,<span class="hljs-function"> -></span> $<span class="hljs-number">1.</span>concat $<span class="hljs-number">2</span>
]</pre></div></div>
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<p>An individual <strong>When</strong> clause, with action.</p>
</div>
<div class="content"><div class='highlight'><pre> <span class="hljs-attribute">When</span>: [
o <span class="hljs-string">'LEADING_WHEN SimpleArgs Block'</span>,<span class="hljs-function"> -></span> [[$<span class="hljs-number">2</span>, $<span class="hljs-number">3</span>]]
o <span class="hljs-string">'LEADING_WHEN SimpleArgs Block TERMINATOR'</span>,<span class="hljs-function"> -></span> [[$<span class="hljs-number">2</span>, $<span class="hljs-number">3</span>]]
]</pre></div></div>
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<p>The most basic form of <em>if</em> is a condition and an action. The following
if-related rules are broken up along these lines in order to avoid
ambiguity.</p>
</div>
<div class="content"><div class='highlight'><pre> <span class="hljs-attribute">IfBlock</span>: [
o <span class="hljs-string">'IF Expression Block'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> If $<span class="hljs-number">2</span>, $<span class="hljs-number">3</span>, <span class="hljs-attribute">type</span>: $<span class="hljs-number">1</span>
o <span class="hljs-string">'IfBlock ELSE IF Expression Block'</span>,<span class="hljs-function"> -></span> $<span class="hljs-number">1.</span>addElse LOC(<span class="hljs-number">3</span>,<span class="hljs-number">5</span>) <span class="hljs-keyword">new</span> If $<span class="hljs-number">4</span>, $<span class="hljs-number">5</span>, <span class="hljs-attribute">type</span>: $<span class="hljs-number">3</span>
]</pre></div></div>
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<p>The full complement of <em>if</em> expressions, including postfix one-liner
<em>if</em> and <em>unless</em>.</p>
</div>
<div class="content"><div class='highlight'><pre> <span class="hljs-attribute">If</span>: [
o <span class="hljs-string">'IfBlock'</span>
o <span class="hljs-string">'IfBlock ELSE Block'</span>,<span class="hljs-function"> -></span> $<span class="hljs-number">1.</span>addElse $<span class="hljs-number">3</span>
o <span class="hljs-string">'Statement POST_IF Expression'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> If $<span class="hljs-number">3</span>, LOC(<span class="hljs-number">1</span>)(Block.wrap [$<span class="hljs-number">1</span>]), <span class="hljs-attribute">type</span>: $<span class="hljs-number">2</span>, <span class="hljs-attribute">statement</span>: <span class="hljs-literal">true</span>
o <span class="hljs-string">'Expression POST_IF Expression'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> If $<span class="hljs-number">3</span>, LOC(<span class="hljs-number">1</span>)(Block.wrap [$<span class="hljs-number">1</span>]), <span class="hljs-attribute">type</span>: $<span class="hljs-number">2</span>, <span class="hljs-attribute">statement</span>: <span class="hljs-literal">true</span>
]</pre></div></div>
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<p>Arithmetic and logical operators, working on one or more operands.
Here they are grouped by order of precedence. The actual precedence rules
are defined at the bottom of the page. It would be shorter if we could
combine most of these rules into a single generic <em>Operand OpSymbol Operand</em>
-type rule, but in order to make the precedence binding possible, separate
rules are necessary.</p>
</div>
<div class="content"><div class='highlight'><pre> <span class="hljs-attribute">Operation</span>: [
o <span class="hljs-string">'UNARY Expression'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> Op $<span class="hljs-number">1</span> , $<span class="hljs-number">2</span>
o <span class="hljs-string">'UNARY_MATH Expression'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> Op $<span class="hljs-number">1</span> , $<span class="hljs-number">2</span>
o <span class="hljs-string">'- Expression'</span>, (<span class="hljs-function">-></span> <span class="hljs-keyword">new</span> Op <span class="hljs-string">'-'</span>, $<span class="hljs-number">2</span>), <span class="hljs-attribute">prec</span>: <span class="hljs-string">'UNARY_MATH'</span>
o <span class="hljs-string">'+ Expression'</span>, (<span class="hljs-function">-></span> <span class="hljs-keyword">new</span> Op <span class="hljs-string">'+'</span>, $<span class="hljs-number">2</span>), <span class="hljs-attribute">prec</span>: <span class="hljs-string">'UNARY_MATH'</span>
o <span class="hljs-string">'YIELD Statement'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> Op $<span class="hljs-number">1</span> , $<span class="hljs-number">2</span>
o <span class="hljs-string">'YIELD Expression'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> Op $<span class="hljs-number">1</span> , $<span class="hljs-number">2</span>
o <span class="hljs-string">'YIELD FROM Expression'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> Op $<span class="hljs-number">1.</span>concat($<span class="hljs-number">2</span>) , $<span class="hljs-number">3</span>
o <span class="hljs-string">'-- SimpleAssignable'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> Op <span class="hljs-string">'--'</span>, $<span class="hljs-number">2</span>
o <span class="hljs-string">'++ SimpleAssignable'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> Op <span class="hljs-string">'++'</span>, $<span class="hljs-number">2</span>
o <span class="hljs-string">'SimpleAssignable --'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> Op <span class="hljs-string">'--'</span>, $<span class="hljs-number">1</span>, <span class="hljs-literal">null</span>, <span class="hljs-literal">true</span>
o <span class="hljs-string">'SimpleAssignable ++'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> Op <span class="hljs-string">'++'</span>, $<span class="hljs-number">1</span>, <span class="hljs-literal">null</span>, <span class="hljs-literal">true</span></pre></div></div>
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<p><a href="http://jashkenas.github.com/coffee-script/#existence">The existential operator</a>.</p>
</div>
<div class="content"><div class='highlight'><pre> o <span class="hljs-string">'Expression ?'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> Existence $<span class="hljs-number">1</span>
o <span class="hljs-string">'Expression + Expression'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> Op <span class="hljs-string">'+'</span> , $<span class="hljs-number">1</span>, $<span class="hljs-number">3</span>
o <span class="hljs-string">'Expression - Expression'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> Op <span class="hljs-string">'-'</span> , $<span class="hljs-number">1</span>, $<span class="hljs-number">3</span>
o <span class="hljs-string">'Expression MATH Expression'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> Op $<span class="hljs-number">2</span>, $<span class="hljs-number">1</span>, $<span class="hljs-number">3</span>
o <span class="hljs-string">'Expression ** Expression'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> Op $<span class="hljs-number">2</span>, $<span class="hljs-number">1</span>, $<span class="hljs-number">3</span>
o <span class="hljs-string">'Expression SHIFT Expression'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> Op $<span class="hljs-number">2</span>, $<span class="hljs-number">1</span>, $<span class="hljs-number">3</span>
o <span class="hljs-string">'Expression COMPARE Expression'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> Op $<span class="hljs-number">2</span>, $<span class="hljs-number">1</span>, $<span class="hljs-number">3</span>
o <span class="hljs-string">'Expression LOGIC Expression'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> Op $<span class="hljs-number">2</span>, $<span class="hljs-number">1</span>, $<span class="hljs-number">3</span>
o <span class="hljs-string">'Expression RELATION Expression'</span>,<span class="hljs-function"> -></span>
<span class="hljs-keyword">if</span> $<span class="hljs-number">2.</span>charAt(<span class="hljs-number">0</span>) <span class="hljs-keyword">is</span> <span class="hljs-string">'!'</span>
<span class="hljs-keyword">new</span> Op($<span class="hljs-number">2</span>[<span class="hljs-number">1.</span>.], $<span class="hljs-number">1</span>, $<span class="hljs-number">3</span>).invert()
<span class="hljs-keyword">else</span>
<span class="hljs-keyword">new</span> Op $<span class="hljs-number">2</span>, $<span class="hljs-number">1</span>, $<span class="hljs-number">3</span>
o <span class="hljs-string">'SimpleAssignable COMPOUND_ASSIGN
Expression'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> Assign $<span class="hljs-number">1</span>, $<span class="hljs-number">3</span>, $<span class="hljs-number">2</span>
o <span class="hljs-string">'SimpleAssignable COMPOUND_ASSIGN
INDENT Expression OUTDENT'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> Assign $<span class="hljs-number">1</span>, $<span class="hljs-number">4</span>, $<span class="hljs-number">2</span>
o <span class="hljs-string">'SimpleAssignable COMPOUND_ASSIGN TERMINATOR
Expression'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> Assign $<span class="hljs-number">1</span>, $<span class="hljs-number">4</span>, $<span class="hljs-number">2</span>
o <span class="hljs-string">'SimpleAssignable EXTENDS Expression'</span>,<span class="hljs-function"> -></span> <span class="hljs-keyword">new</span> Extends $<span class="hljs-number">1</span>, $<span class="hljs-number">3</span>
]</pre></div></div>
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<h2 id="precedence">Precedence</h2>
</div>
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<p>Operators at the top of this list have higher precedence than the ones lower
down. Following these rules is what makes <code>2 + 3 * 4</code> parse as:</p>
<pre><code><span class="hljs-number">2</span> + (<span class="hljs-number">3</span> * <span class="hljs-number">4</span>)
</code></pre><p>And not:</p>
<pre><code>(<span class="hljs-number">2</span> + <span class="hljs-number">3</span>) * <span class="hljs-number">4</span>
</code></pre>
</div>
<div class="content"><div class='highlight'><pre>operators = [
[<span class="hljs-string">'left'</span>, <span class="hljs-string">'.'</span>, <span class="hljs-string">'?.'</span>, <span class="hljs-string">'::'</span>, <span class="hljs-string">'?::'</span>]
[<span class="hljs-string">'left'</span>, <span class="hljs-string">'CALL_START'</span>, <span class="hljs-string">'CALL_END'</span>]
[<span class="hljs-string">'nonassoc'</span>, <span class="hljs-string">'++'</span>, <span class="hljs-string">'--'</span>]
[<span class="hljs-string">'left'</span>, <span class="hljs-string">'?'</span>]
[<span class="hljs-string">'right'</span>, <span class="hljs-string">'UNARY'</span>]
[<span class="hljs-string">'right'</span>, <span class="hljs-string">'**'</span>]
[<span class="hljs-string">'right'</span>, <span class="hljs-string">'UNARY_MATH'</span>]
[<span class="hljs-string">'left'</span>, <span class="hljs-string">'MATH'</span>]
[<span class="hljs-string">'left'</span>, <span class="hljs-string">'+'</span>, <span class="hljs-string">'-'</span>]
[<span class="hljs-string">'left'</span>, <span class="hljs-string">'SHIFT'</span>]
[<span class="hljs-string">'left'</span>, <span class="hljs-string">'RELATION'</span>]
[<span class="hljs-string">'left'</span>, <span class="hljs-string">'COMPARE'</span>]
[<span class="hljs-string">'left'</span>, <span class="hljs-string">'LOGIC'</span>]
[<span class="hljs-string">'nonassoc'</span>, <span class="hljs-string">'INDENT'</span>, <span class="hljs-string">'OUTDENT'</span>]
[<span class="hljs-string">'right'</span>, <span class="hljs-string">'YIELD'</span>]
[<span class="hljs-string">'right'</span>, <span class="hljs-string">'='</span>, <span class="hljs-string">':'</span>, <span class="hljs-string">'COMPOUND_ASSIGN'</span>, <span class="hljs-string">'RETURN'</span>, <span class="hljs-string">'THROW'</span>, <span class="hljs-string">'EXTENDS'</span>]
[<span class="hljs-string">'right'</span>, <span class="hljs-string">'FORIN'</span>, <span class="hljs-string">'FOROF'</span>, <span class="hljs-string">'BY'</span>, <span class="hljs-string">'WHEN'</span>]
[<span class="hljs-string">'right'</span>, <span class="hljs-string">'IF'</span>, <span class="hljs-string">'ELSE'</span>, <span class="hljs-string">'FOR'</span>, <span class="hljs-string">'WHILE'</span>, <span class="hljs-string">'UNTIL'</span>, <span class="hljs-string">'LOOP'</span>, <span class="hljs-string">'SUPER'</span>, <span class="hljs-string">'CLASS'</span>]
[<span class="hljs-string">'left'</span>, <span class="hljs-string">'POST_IF'</span>]
]</pre></div></div>
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<h2 id="wrapping-up">Wrapping Up</h2>
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<p>Finally, now that we have our <strong>grammar</strong> and our <strong>operators</strong>, we can create
our <strong>Jison.Parser</strong>. We do this by processing all of our rules, recording all
terminals (every symbol which does not appear as the name of a rule above)
as “tokens”.</p>
</div>
<div class="content"><div class='highlight'><pre>tokens = []
<span class="hljs-keyword">for</span> name, alternatives <span class="hljs-keyword">of</span> grammar
grammar[name] = <span class="hljs-keyword">for</span> alt <span class="hljs-keyword">in</span> alternatives
<span class="hljs-keyword">for</span> token <span class="hljs-keyword">in</span> alt[<span class="hljs-number">0</span>].split <span class="hljs-string">' '</span>
tokens.push token <span class="hljs-keyword">unless</span> grammar[token]
alt[<span class="hljs-number">1</span>] = <span class="hljs-string">"return <span class="hljs-subst">#{alt[<span class="hljs-number">1</span>]}</span>"</span> <span class="hljs-keyword">if</span> name <span class="hljs-keyword">is</span> <span class="hljs-string">'Root'</span>
alt</pre></div></div>
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<p>Initialize the <strong>Parser</strong> with our list of terminal <strong>tokens</strong>, our <strong>grammar</strong>
rules, and the name of the root. Reverse the operators because Jison orders
precedence from low to high, and we have it high to low
(as in <a href="http://dinosaur.compilertools.net/yacc/index.html">Yacc</a>).</p>
</div>
<div class="content"><div class='highlight'><pre><span class="hljs-built_in">exports</span>.parser = <span class="hljs-keyword">new</span> Parser
tokens : tokens.join <span class="hljs-string">' '</span>
bnf : grammar
operators : operators.reverse()
startSymbol : <span class="hljs-string">'Root'</span></pre></div></div>
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