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<title>src/full/Agda/Syntax/Parser/Comments.hs</title>
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<pre><a name="line-1"></a><span class='hs-comment'>{-# LANGUAGE CPP #-}</span>
<a name="line-2"></a>
<a name="line-3"></a><span class='hs-comment'>{-| This module defines the lex action to lex nested comments. As is well-known
<a name="line-4"></a> this cannot be done by regular expressions (which, incidently, is probably
<a name="line-5"></a> the reason why C-comments don't nest).
<a name="line-6"></a>
<a name="line-7"></a> When scanning nested comments we simply keep track of the nesting level,
<a name="line-8"></a> counting up for /open comments/ and down for /close comments/.
<a name="line-9"></a>-}</span>
<a name="line-10"></a><span class='hs-keyword'>module</span> <span class='hs-conid'>Agda</span><span class='hs-varop'>.</span><span class='hs-conid'>Syntax</span><span class='hs-varop'>.</span><span class='hs-conid'>Parser</span><span class='hs-varop'>.</span><span class='hs-conid'>Comments</span>
<a name="line-11"></a> <span class='hs-keyword'>where</span>
<a name="line-12"></a>
<a name="line-13"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Data</span><span class='hs-varop'>.</span><span class='hs-conid'>List</span>
<a name="line-14"></a>
<a name="line-15"></a><span class='hs-keyword'>import</span> <span class='hs-comment'>{-# SOURCE #-}</span> <span class='hs-conid'>Agda</span><span class='hs-varop'>.</span><span class='hs-conid'>Syntax</span><span class='hs-varop'>.</span><span class='hs-conid'>Parser</span><span class='hs-varop'>.</span><span class='hs-conid'>LexActions</span>
<a name="line-16"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Agda</span><span class='hs-varop'>.</span><span class='hs-conid'>Syntax</span><span class='hs-varop'>.</span><span class='hs-conid'>Parser</span><span class='hs-varop'>.</span><span class='hs-conid'>Monad</span>
<a name="line-17"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Agda</span><span class='hs-varop'>.</span><span class='hs-conid'>Syntax</span><span class='hs-varop'>.</span><span class='hs-conid'>Parser</span><span class='hs-varop'>.</span><span class='hs-conid'>Tokens</span>
<a name="line-18"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Agda</span><span class='hs-varop'>.</span><span class='hs-conid'>Syntax</span><span class='hs-varop'>.</span><span class='hs-conid'>Parser</span><span class='hs-varop'>.</span><span class='hs-conid'>Alex</span>
<a name="line-19"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Agda</span><span class='hs-varop'>.</span><span class='hs-conid'>Syntax</span><span class='hs-varop'>.</span><span class='hs-conid'>Parser</span><span class='hs-varop'>.</span><span class='hs-conid'>LookAhead</span>
<a name="line-20"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Agda</span><span class='hs-varop'>.</span><span class='hs-conid'>Syntax</span><span class='hs-varop'>.</span><span class='hs-conid'>Position</span>
<a name="line-21"></a>
<a name="line-22"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Agda</span><span class='hs-varop'>.</span><span class='hs-conid'>Utils</span><span class='hs-varop'>.</span><span class='hs-conid'>Monad</span>
<a name="line-23"></a>
<a name="line-24"></a><span class='hs-cpp'>#include "../../undefined.h"</span>
<a name="line-25"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Agda</span><span class='hs-varop'>.</span><span class='hs-conid'>Utils</span><span class='hs-varop'>.</span><span class='hs-conid'>Impossible</span>
<a name="line-26"></a>
<a name="line-27"></a><span class='hs-comment'>-- | Should comment tokens be output?</span>
<a name="line-28"></a>
<a name="line-29"></a><a name="keepComments"></a><span class='hs-definition'>keepComments</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>LexPredicate</span>
<a name="line-30"></a><span class='hs-definition'>keepComments</span> <span class='hs-layout'>(</span><span class='hs-keyword'>_</span><span class='hs-layout'>,</span> <span class='hs-varid'>s</span><span class='hs-layout'>)</span> <span class='hs-keyword'>_</span> <span class='hs-keyword'>_</span> <span class='hs-keyword'>_</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>parseKeepComments</span> <span class='hs-varid'>s</span>
<a name="line-31"></a>
<a name="line-32"></a><span class='hs-comment'>-- | Should comment tokens be output?</span>
<a name="line-33"></a>
<a name="line-34"></a><a name="keepCommentsM"></a><span class='hs-definition'>keepCommentsM</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>Parser</span> <span class='hs-conid'>Bool</span>
<a name="line-35"></a><span class='hs-definition'>keepCommentsM</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>fmap</span> <span class='hs-varid'>parseKeepComments</span> <span class='hs-varid'>getParseFlags</span>
<a name="line-36"></a>
<a name="line-37"></a><a name="nestedComment"></a><span class='hs-comment'>-- | Manually lexing a block comment. Assumes an /open comment/ has been lexed.</span>
<a name="line-38"></a><span class='hs-comment'>-- In the end the comment is discarded and 'lexToken' is called to lex a real</span>
<a name="line-39"></a><span class='hs-comment'>-- token.</span>
<a name="line-40"></a><span class='hs-definition'>nestedComment</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>LexAction</span> <span class='hs-conid'>Token</span>
<a name="line-41"></a><span class='hs-definition'>nestedComment</span> <span class='hs-varid'>inp</span> <span class='hs-varid'>inp'</span> <span class='hs-keyword'>_</span> <span class='hs-keyglyph'>=</span>
<a name="line-42"></a> <span class='hs-keyword'>do</span> <span class='hs-varid'>setLexInput</span> <span class='hs-varid'>inp'</span>
<a name="line-43"></a> <span class='hs-varid'>runLookAhead</span> <span class='hs-varid'>err</span> <span class='hs-varop'>$</span> <span class='hs-varid'>skipBlock</span> <span class='hs-str'>"{-"</span> <span class='hs-str'>"-}"</span>
<a name="line-44"></a> <span class='hs-varid'>keep</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>keepCommentsM</span>
<a name="line-45"></a> <span class='hs-keyword'>if</span> <span class='hs-varid'>keep</span> <span class='hs-keyword'>then</span> <span class='hs-keyword'>do</span>
<a name="line-46"></a> <span class='hs-varid'>inp''</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>getLexInput</span>
<a name="line-47"></a> <span class='hs-keyword'>let</span> <span class='hs-varid'>p1</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>lexPos</span> <span class='hs-varid'>inp</span><span class='hs-layout'>;</span> <span class='hs-varid'>p2</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>lexPos</span> <span class='hs-varid'>inp''</span>
<a name="line-48"></a> <span class='hs-varid'>i</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Interval</span> <span class='hs-varid'>p1</span> <span class='hs-varid'>p2</span>
<a name="line-49"></a> <span class='hs-varid'>s</span> <span class='hs-keyglyph'>=</span> <span class='hs-keyword'>case</span> <span class='hs-layout'>(</span><span class='hs-varid'>p1</span><span class='hs-layout'>,</span> <span class='hs-varid'>p2</span><span class='hs-layout'>)</span> <span class='hs-keyword'>of</span>
<a name="line-50"></a> <span class='hs-layout'>(</span><span class='hs-conid'>Pn</span> <span class='hs-layout'>{</span> <span class='hs-varid'>posPos</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>p1</span> <span class='hs-layout'>}</span><span class='hs-layout'>,</span> <span class='hs-conid'>Pn</span> <span class='hs-layout'>{</span> <span class='hs-varid'>posPos</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>p2</span> <span class='hs-layout'>}</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>-></span>
<a name="line-51"></a> <span class='hs-varid'>genericTake</span> <span class='hs-layout'>(</span><span class='hs-varid'>p2</span> <span class='hs-comment'>-</span> <span class='hs-varid'>p1</span><span class='hs-layout'>)</span> <span class='hs-varop'>$</span> <span class='hs-varid'>lexInput</span> <span class='hs-varid'>inp</span>
<a name="line-52"></a> <span class='hs-varid'>return</span> <span class='hs-varop'>$</span> <span class='hs-conid'>TokComment</span> <span class='hs-layout'>(</span><span class='hs-varid'>i</span><span class='hs-layout'>,</span> <span class='hs-varid'>s</span><span class='hs-layout'>)</span>
<a name="line-53"></a> <span class='hs-keyword'>else</span>
<a name="line-54"></a> <span class='hs-varid'>lexToken</span>
<a name="line-55"></a> <span class='hs-keyword'>where</span>
<a name="line-56"></a> <span class='hs-varid'>err</span> <span class='hs-keyword'>_</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>liftP</span> <span class='hs-varop'>$</span> <span class='hs-varid'>parseErrorAt</span> <span class='hs-layout'>(</span><span class='hs-varid'>lexPos</span> <span class='hs-varid'>inp</span><span class='hs-layout'>)</span> <span class='hs-str'>"Unterminated '{-'"</span>
<a name="line-57"></a>
<a name="line-58"></a><a name="hole"></a><span class='hs-comment'>-- | Lex a hole (@{! ... !}@). Holes can be nested.</span>
<a name="line-59"></a><span class='hs-comment'>-- Returns @'TokSymbol' 'SymQuestionMark'@.</span>
<a name="line-60"></a><span class='hs-definition'>hole</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>LexAction</span> <span class='hs-conid'>Token</span>
<a name="line-61"></a><span class='hs-definition'>hole</span> <span class='hs-varid'>inp</span> <span class='hs-varid'>inp'</span> <span class='hs-keyword'>_</span> <span class='hs-keyglyph'>=</span>
<a name="line-62"></a> <span class='hs-keyword'>do</span> <span class='hs-varid'>setLexInput</span> <span class='hs-varid'>inp'</span>
<a name="line-63"></a> <span class='hs-varid'>runLookAhead</span> <span class='hs-varid'>err</span> <span class='hs-varop'>$</span> <span class='hs-varid'>skipBlock</span> <span class='hs-str'>"{!"</span> <span class='hs-str'>"!}"</span>
<a name="line-64"></a> <span class='hs-varid'>p</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>lexPos</span> <span class='hs-varop'><$></span> <span class='hs-varid'>getLexInput</span>
<a name="line-65"></a> <span class='hs-varid'>return</span> <span class='hs-varop'>$</span> <span class='hs-conid'>TokSymbol</span> <span class='hs-conid'>SymQuestionMark</span> <span class='hs-layout'>(</span><span class='hs-conid'>Interval</span> <span class='hs-layout'>(</span><span class='hs-varid'>lexPos</span> <span class='hs-varid'>inp</span><span class='hs-layout'>)</span> <span class='hs-varid'>p</span><span class='hs-layout'>)</span>
<a name="line-66"></a> <span class='hs-keyword'>where</span>
<a name="line-67"></a> <span class='hs-varid'>err</span> <span class='hs-keyword'>_</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>liftP</span> <span class='hs-varop'>$</span> <span class='hs-varid'>parseErrorAt</span> <span class='hs-layout'>(</span><span class='hs-varid'>lexPos</span> <span class='hs-varid'>inp</span><span class='hs-layout'>)</span> <span class='hs-str'>"Unterminated '{!'"</span>
<a name="line-68"></a>
<a name="line-69"></a><a name="skipBlock"></a><span class='hs-comment'>-- | Skip a block of text enclosed by the given open and close strings. Assumes</span>
<a name="line-70"></a><span class='hs-comment'>-- the first open string has been consumed. Open-close pairs may be nested.</span>
<a name="line-71"></a><span class='hs-definition'>skipBlock</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>String</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>String</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>LookAhead</span> <span class='hs-conid'>()</span>
<a name="line-72"></a><span class='hs-definition'>skipBlock</span> <span class='hs-varid'>open</span> <span class='hs-varid'>close</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>scan</span> <span class='hs-num'>1</span>
<a name="line-73"></a> <span class='hs-keyword'>where</span>
<a name="line-74"></a> <span class='hs-varid'>scan</span> <span class='hs-num'>0</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>sync</span>
<a name="line-75"></a> <span class='hs-varid'>scan</span> <span class='hs-varid'>n</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>match</span> <span class='hs-keyglyph'>[</span> <span class='hs-varid'>open</span> <span class='hs-varop'>==></span> <span class='hs-varid'>scan</span> <span class='hs-layout'>(</span><span class='hs-varid'>n</span> <span class='hs-varop'>+</span> <span class='hs-num'>1</span><span class='hs-layout'>)</span>
<a name="line-76"></a> <span class='hs-layout'>,</span> <span class='hs-varid'>close</span> <span class='hs-varop'>==></span> <span class='hs-varid'>scan</span> <span class='hs-layout'>(</span><span class='hs-varid'>n</span> <span class='hs-comment'>-</span> <span class='hs-num'>1</span><span class='hs-layout'>)</span>
<a name="line-77"></a> <span class='hs-keyglyph'>]</span> <span class='hs-varop'>`other`</span> <span class='hs-varid'>scan</span> <span class='hs-varid'>n</span>
<a name="line-78"></a> <span class='hs-keyword'>where</span>
<a name="line-79"></a> <span class='hs-layout'>(</span><span class='hs-varop'>==></span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>(,)</span>
<a name="line-80"></a> <span class='hs-varid'>other</span> <span class='hs-keyglyph'>=</span> <span class='hs-layout'>(</span><span class='hs-varop'>$</span><span class='hs-layout'>)</span>
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