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scope.html
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<!DOCTYPE html> <html> <head> <title>scope.coffee</title> <meta http-equiv="content-type" content="text/html; charset=UTF-8"> <link rel="stylesheet" media="all" href="docco.css" /> </head> <body> <div id="container"> <div id="background"></div> <div id="jump_to"> Jump To … <div id="jump_wrapper"> <div id="jump_page"> <a class="source" href="browser.html"> browser.coffee </a> <a class="source" href="cake.html"> cake.coffee </a> <a class="source" href="coffee-script.html"> coffee-script.coffee </a> <a class="source" href="command.html"> command.coffee </a> <a class="source" href="grammar.html"> grammar.coffee </a> <a class="source" href="helpers.html"> helpers.coffee </a> <a class="source" href="index.html"> index.coffee </a> <a class="source" href="lexer.html"> lexer.coffee </a> <a class="source" href="nodes.html"> nodes.coffee </a> <a class="source" href="optparse.html"> optparse.coffee </a> <a class="source" href="repl.html"> repl.coffee </a> <a class="source" href="rewriter.html"> rewriter.coffee </a> <a class="source" href="scope.html"> scope.coffee </a> </div> </div> </div> <table cellpadding="0" cellspacing="0"> <thead> <tr> <th class="docs"> <h1> scope.coffee </h1> </th> <th class="code"> </th> </tr> </thead> <tbody> <tr id="section-1"> <td class="docs"> <div class="pilwrap"> <a class="pilcrow" href="#section-1">¶</a> </div> <p>The <strong>Scope</strong> class regulates lexical scoping within CoffeeScript. As you
generate code, you create a tree of scopes in the same shape as the nested
function bodies. Each scope knows about the variables declared within it,
and has a reference to its parent enclosing scope. In this way, we know which
variables are new and need to be declared with <code>var</code>, and which are shared
with the outside.</p> </td> <td class="code"> <div class="highlight"><pre></pre></div> </td> </tr> <tr id="section-2"> <td class="docs"> <div class="pilwrap"> <a class="pilcrow" href="#section-2">¶</a> </div> <p>Import the helpers we plan to use.</p> </td> <td class="code"> <div class="highlight"><pre><span class="p">{</span><span class="nx">extend</span><span class="p">,</span> <span class="nx">last</span><span class="p">}</span> <span class="o">=</span> <span class="nx">require</span> <span class="s1">'./helpers'</span>
<span class="nv">exports.Scope = </span><span class="nx">class</span> <span class="nx">Scope</span></pre></div> </td> </tr> <tr id="section-3"> <td class="docs"> <div class="pilwrap"> <a class="pilcrow" href="#section-3">¶</a> </div> <p>The top-level <strong>Scope</strong> object.</p> </td> <td class="code"> <div class="highlight"><pre> <span class="nx">@root</span><span class="o">:</span> <span class="kc">null</span></pre></div> </td> </tr> <tr id="section-4"> <td class="docs"> <div class="pilwrap"> <a class="pilcrow" href="#section-4">¶</a> </div> <p>Initialize a scope with its parent, for lookups up the chain,
as well as a reference to the <strong>Block</strong> node it belongs to, which is
where it should declare its variables, and a reference to the function that
it wraps.</p> </td> <td class="code"> <div class="highlight"><pre> <span class="nx">constructor</span><span class="o">:</span> <span class="p">(</span><span class="nx">@parent</span><span class="p">,</span> <span class="nx">@expressions</span><span class="p">,</span> <span class="nx">@method</span><span class="p">)</span> <span class="o">-></span>
<span class="vi">@variables = </span><span class="p">[{</span><span class="nx">name</span><span class="o">:</span> <span class="s1">'arguments'</span><span class="p">,</span> <span class="nx">type</span><span class="o">:</span> <span class="s1">'arguments'</span><span class="p">}]</span>
<span class="vi">@positions = </span><span class="p">{}</span>
<span class="nv">Scope.root = </span><span class="k">this</span> <span class="nx">unless</span> <span class="nx">@parent</span></pre></div> </td> </tr> <tr id="section-5"> <td class="docs"> <div class="pilwrap"> <a class="pilcrow" href="#section-5">¶</a> </div> <p>Adds a new variable or overrides an existing one.</p> </td> <td class="code"> <div class="highlight"><pre> <span class="nx">add</span><span class="o">:</span> <span class="p">(</span><span class="nx">name</span><span class="p">,</span> <span class="nx">type</span><span class="p">,</span> <span class="nx">immediate</span><span class="p">)</span> <span class="o">-></span>
<span class="k">return</span> <span class="nx">@parent</span><span class="p">.</span><span class="nx">add</span> <span class="nx">name</span><span class="p">,</span> <span class="nx">type</span><span class="p">,</span> <span class="nx">immediate</span> <span class="k">if</span> <span class="nx">@shared</span> <span class="o">and</span> <span class="o">not</span> <span class="nx">immediate</span>
<span class="k">if</span> <span class="k">typeof</span> <span class="p">(</span><span class="nv">pos = </span><span class="nx">@positions</span><span class="p">[</span><span class="nx">name</span><span class="p">])</span> <span class="o">is</span> <span class="s1">'number'</span>
<span class="nx">@variables</span><span class="p">[</span><span class="nx">pos</span><span class="p">].</span><span class="nv">type = </span><span class="nx">type</span>
<span class="k">else</span>
<span class="nx">@positions</span><span class="p">[</span><span class="nx">name</span><span class="p">]</span> <span class="o">=</span> <span class="nx">@variables</span><span class="p">.</span><span class="nx">push</span><span class="p">({</span><span class="nx">name</span><span class="p">,</span> <span class="nx">type</span><span class="p">})</span> <span class="o">-</span> <span class="mi">1</span></pre></div> </td> </tr> <tr id="section-6"> <td class="docs"> <div class="pilwrap"> <a class="pilcrow" href="#section-6">¶</a> </div> <p>Look up a variable name in lexical scope, and declare it if it does not
already exist.</p> </td> <td class="code"> <div class="highlight"><pre> <span class="nx">find</span><span class="o">:</span> <span class="p">(</span><span class="nx">name</span><span class="p">,</span> <span class="nx">options</span><span class="p">)</span> <span class="o">-></span>
<span class="k">return</span> <span class="kc">yes</span> <span class="k">if</span> <span class="nx">@check</span> <span class="nx">name</span><span class="p">,</span> <span class="nx">options</span>
<span class="nx">@add</span> <span class="nx">name</span><span class="p">,</span> <span class="s1">'var'</span>
<span class="kc">no</span></pre></div> </td> </tr> <tr id="section-7"> <td class="docs"> <div class="pilwrap"> <a class="pilcrow" href="#section-7">¶</a> </div> <p>Reserve a variable name as originating from a function parameter for this
scope. No <code>var</code> required for internal references.</p> </td> <td class="code"> <div class="highlight"><pre> <span class="nx">parameter</span><span class="o">:</span> <span class="p">(</span><span class="nx">name</span><span class="p">)</span> <span class="o">-></span>
<span class="k">return</span> <span class="k">if</span> <span class="nx">@shared</span> <span class="o">and</span> <span class="nx">@parent</span><span class="p">.</span><span class="nx">check</span> <span class="nx">name</span><span class="p">,</span> <span class="kc">yes</span>
<span class="nx">@add</span> <span class="nx">name</span><span class="p">,</span> <span class="s1">'param'</span></pre></div> </td> </tr> <tr id="section-8"> <td class="docs"> <div class="pilwrap"> <a class="pilcrow" href="#section-8">¶</a> </div> <p>Just check to see if a variable has already been declared, without reserving,
walks up to the root scope.</p> </td> <td class="code"> <div class="highlight"><pre> <span class="nx">check</span><span class="o">:</span> <span class="p">(</span><span class="nx">name</span><span class="p">,</span> <span class="nx">immediate</span><span class="p">)</span> <span class="o">-></span>
<span class="nv">found = </span><span class="o">!!</span><span class="nx">@type</span><span class="p">(</span><span class="nx">name</span><span class="p">)</span>
<span class="k">return</span> <span class="nx">found</span> <span class="k">if</span> <span class="nx">found</span> <span class="o">or</span> <span class="nx">immediate</span>
<span class="o">!!</span><span class="nx">@parent</span><span class="o">?</span><span class="p">.</span><span class="nx">check</span> <span class="nx">name</span></pre></div> </td> </tr> <tr id="section-9"> <td class="docs"> <div class="pilwrap"> <a class="pilcrow" href="#section-9">¶</a> </div> <p>Generate a temporary variable name at the given index.</p> </td> <td class="code"> <div class="highlight"><pre> <span class="nx">temporary</span><span class="o">:</span> <span class="p">(</span><span class="nx">name</span><span class="p">,</span> <span class="nx">index</span><span class="p">)</span> <span class="o">-></span>
<span class="k">if</span> <span class="nx">name</span><span class="p">.</span><span class="nx">length</span> <span class="o">></span> <span class="mi">1</span>
<span class="s1">'_'</span> <span class="o">+</span> <span class="nx">name</span> <span class="o">+</span> <span class="k">if</span> <span class="nx">index</span> <span class="o">></span> <span class="mi">1</span> <span class="k">then</span> <span class="nx">index</span> <span class="k">else</span> <span class="s1">''</span>
<span class="k">else</span>
<span class="s1">'_'</span> <span class="o">+</span> <span class="p">(</span><span class="nx">index</span> <span class="o">+</span> <span class="nb">parseInt</span> <span class="nx">name</span><span class="p">,</span> <span class="mi">36</span><span class="p">).</span><span class="nx">toString</span><span class="p">(</span><span class="mi">36</span><span class="p">).</span><span class="nx">replace</span> <span class="sr">/\d/g</span><span class="p">,</span> <span class="s1">'a'</span></pre></div> </td> </tr> <tr id="section-10"> <td class="docs"> <div class="pilwrap"> <a class="pilcrow" href="#section-10">¶</a> </div> <p>Gets the type of a variable.</p> </td> <td class="code"> <div class="highlight"><pre> <span class="nx">type</span><span class="o">:</span> <span class="p">(</span><span class="nx">name</span><span class="p">)</span> <span class="o">-></span>
<span class="k">return</span> <span class="nx">v</span><span class="p">.</span><span class="nx">type</span> <span class="k">for</span> <span class="nx">v</span> <span class="k">in</span> <span class="nx">@variables</span> <span class="k">when</span> <span class="nx">v</span><span class="p">.</span><span class="nx">name</span> <span class="o">is</span> <span class="nx">name</span>
<span class="kc">null</span></pre></div> </td> </tr> <tr id="section-11"> <td class="docs"> <div class="pilwrap"> <a class="pilcrow" href="#section-11">¶</a> </div> <p>If we need to store an intermediate result, find an available name for a
compiler-generated variable. <code>_var</code>, <code>_var2</code>, and so on...</p> </td> <td class="code"> <div class="highlight"><pre> <span class="nx">freeVariable</span><span class="o">:</span> <span class="p">(</span><span class="nx">type</span><span class="p">)</span> <span class="o">-></span>
<span class="nv">index = </span><span class="mi">0</span>
<span class="nx">index</span><span class="o">++</span> <span class="k">while</span> <span class="nx">@check</span><span class="p">((</span><span class="nv">temp = </span><span class="nx">@temporary</span> <span class="nx">type</span><span class="p">,</span> <span class="nx">index</span><span class="p">))</span>
<span class="nx">@add</span> <span class="nx">temp</span><span class="p">,</span> <span class="s1">'var'</span><span class="p">,</span> <span class="kc">yes</span>
<span class="nx">temp</span></pre></div> </td> </tr> <tr id="section-12"> <td class="docs"> <div class="pilwrap"> <a class="pilcrow" href="#section-12">¶</a> </div> <p>Ensure that an assignment is made at the top of this scope
(or at the top-level scope, if requested).</p> </td> <td class="code"> <div class="highlight"><pre> <span class="nx">assign</span><span class="o">:</span> <span class="p">(</span><span class="nx">name</span><span class="p">,</span> <span class="nx">value</span><span class="p">)</span> <span class="o">-></span>
<span class="nx">@add</span> <span class="nx">name</span><span class="p">,</span> <span class="nx">value</span><span class="o">:</span> <span class="nx">value</span><span class="p">,</span> <span class="nx">assigned</span><span class="o">:</span> <span class="kc">true</span>
<span class="vi">@hasAssignments = </span><span class="kc">yes</span></pre></div> </td> </tr> <tr id="section-13"> <td class="docs"> <div class="pilwrap"> <a class="pilcrow" href="#section-13">¶</a> </div> <p>Does this scope have any declared variables?</p> </td> <td class="code"> <div class="highlight"><pre> <span class="nx">hasDeclarations</span><span class="o">:</span> <span class="o">-></span>
<span class="o">!!</span><span class="nx">@declaredVariables</span><span class="p">().</span><span class="nx">length</span></pre></div> </td> </tr> <tr id="section-14"> <td class="docs"> <div class="pilwrap"> <a class="pilcrow" href="#section-14">¶</a> </div> <p>Return the list of variables first declared in this scope.</p> </td> <td class="code"> <div class="highlight"><pre> <span class="nx">declaredVariables</span><span class="o">:</span> <span class="o">-></span>
<span class="nv">realVars = </span><span class="p">[]</span>
<span class="nv">tempVars = </span><span class="p">[]</span>
<span class="k">for</span> <span class="nx">v</span> <span class="k">in</span> <span class="nx">@variables</span> <span class="k">when</span> <span class="nx">v</span><span class="p">.</span><span class="nx">type</span> <span class="o">is</span> <span class="s1">'var'</span>
<span class="p">(</span><span class="k">if</span> <span class="nx">v</span><span class="p">.</span><span class="nx">name</span><span class="p">.</span><span class="nx">charAt</span><span class="p">(</span><span class="mi">0</span><span class="p">)</span> <span class="o">is</span> <span class="s1">'_'</span> <span class="k">then</span> <span class="nx">tempVars</span> <span class="k">else</span> <span class="nx">realVars</span><span class="p">).</span><span class="nx">push</span> <span class="nx">v</span><span class="p">.</span><span class="nx">name</span>
<span class="nx">realVars</span><span class="p">.</span><span class="nx">sort</span><span class="p">().</span><span class="nx">concat</span> <span class="nx">tempVars</span><span class="p">.</span><span class="nx">sort</span><span class="p">()</span></pre></div> </td> </tr> <tr id="section-15"> <td class="docs"> <div class="pilwrap"> <a class="pilcrow" href="#section-15">¶</a> </div> <p>Return the list of assignments that are supposed to be made at the top
of this scope.</p> </td> <td class="code"> <div class="highlight"><pre> <span class="nx">assignedVariables</span><span class="o">:</span> <span class="o">-></span>
<span class="s2">"#{v.name} = #{v.type.value}"</span> <span class="k">for</span> <span class="nx">v</span> <span class="k">in</span> <span class="nx">@variables</span> <span class="k">when</span> <span class="nx">v</span><span class="p">.</span><span class="nx">type</span><span class="p">.</span><span class="nx">assigned</span>
</pre></div> </td> </tr> </tbody> </table> </div> </body> </html>