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<head><title>Option -- the class of all pairs x => y</title>
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<div><h1>Option -- the class of all pairs x => y</h1>
<div class="single"><h2>Description</h2>
<div><p/>
Such pairs are used as optional arguments for functions. There is also a way to make new hash tables with <a href="_new.html" title="new objects and new types">new</a> by providing a list of option pairs.<p/>
<table class="examples"><tr><td><pre>i1 : a => 5
o1 = a => 5
o1 : Option</pre>
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<tr><td><pre>i2 : peek (a => 5)
o2 = Option{a, 5}</pre>
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<tr><td><pre>i3 : new HashTable from {a => 5, b => 7}
o3 = HashTable{a => 5}
b => 7
o3 : HashTable</pre>
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<p/>
These pairs are implemented as lists, so that if <tt>z</tt> is <tt>x => y</tt>, then <tt>x</tt> is <tt>z#0</tt> and <tt>y</tt> is <tt>z#1</tt>.<p/>
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<div class="single"><h2>See also</h2>
<ul><li><span><a href="__eq_gt.html" title="produce an Option">=></a> -- produce an Option</span></li>
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<div class="waystouse"><h2>Functions and methods returning an option :</h2>
<ul><li><span>Thing => Thing, see <span><a href="__eq_gt.html" title="produce an Option">=></a> -- produce an Option</span></span></li>
</ul>
<h2>Methods that use an option :</h2>
<ul><li><span>directSum(Option), see <span><a href="_direct__Sum.html" title="direct sum of modules or maps">directSum</a> -- direct sum of modules or maps</span></span></li>
<li><span>Option ++ Option, see <span><a href="_direct__Sum.html" title="direct sum of modules or maps">directSum</a> -- direct sum of modules or maps</span></span></li>
<li><span>installAssignmentMethod(Symbol,HashTable,HashTable,Option), see <span><a href="_install__Assignment__Method.html" title="install methods assignment to the value of an operator">installAssignmentMethod</a> -- install methods assignment to the value of an operator</span></span></li>
<li><span>installAssignmentMethod(Symbol,HashTable,Option), see <span><a href="_install__Assignment__Method.html" title="install methods assignment to the value of an operator">installAssignmentMethod</a> -- install methods assignment to the value of an operator</span></span></li>
<li><span>substitute(Ideal,Option), see <span><a href="_substitute.html" title="substituting values for variables">substitute</a> -- substituting values for variables</span></span></li>
<li><span>substitute(Matrix,Option), see <span><a href="_substitute.html" title="substituting values for variables">substitute</a> -- substituting values for variables</span></span></li>
<li><span>substitute(Module,Option), see <span><a href="_substitute.html" title="substituting values for variables">substitute</a> -- substituting values for variables</span></span></li>
<li><span>substitute(RingElement,Option), see <span><a href="_substitute.html" title="substituting values for variables">substitute</a> -- substituting values for variables</span></span></li>
<li><span>substitute(Vector,Option), see <span><a href="_substitute.html" title="substituting values for variables">substitute</a> -- substituting values for variables</span></span></li>
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<div class="waystouse"><h2>For the programmer</h2>
<p>The object <a href="___Option.html" title="the class of all pairs x => y">Option</a> is <span>a <a href="___Type.html">type</a></span>, with ancestor classes <a href="___Basic__List.html" title="the class of all basic lists">BasicList</a> < <a href="___Thing.html" title="the class of all things">Thing</a>.</p>
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