396 lines
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HTML
396 lines
18 KiB
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<ul class="sections">
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<li id="title">
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<div class="annotation">
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<h1>scope.litcoffee</h1>
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</div>
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</li>
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<li id="section-1">
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<div class="annotation">
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<div class="pilwrap ">
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<a class="pilcrow" href="#section-1">¶</a>
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</div>
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<p>The <strong>Scope</strong> class regulates lexical scoping within CoffeeScript. As you
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generate code, you create a tree of scopes in the same shape as the nested
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function bodies. Each scope knows about the variables declared within it,
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and has a reference to its parent enclosing scope. In this way, we know which
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variables are new and need to be declared with <code>var</code>, and which are shared
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with external scopes.</p>
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<p>Import the helpers we plan to use.</p>
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</div>
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<div class="content"><div class='highlight'><pre>{extend, last} = <span class="hljs-built_in">require</span> <span class="hljs-string">'./helpers'</span>
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<span class="hljs-built_in">exports</span>.Scope = <span class="hljs-class"><span class="hljs-keyword">class</span> <span class="hljs-title">Scope</span></span></pre></div></div>
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</li>
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<li id="section-2">
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<div class="annotation">
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<div class="pilwrap ">
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<a class="pilcrow" href="#section-2">¶</a>
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</div>
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<p>The <code>root</code> is the top-level <strong>Scope</strong> object for a given file.</p>
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</div>
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<div class="content"><div class='highlight'><pre> <span class="hljs-property">@root</span>: <span class="hljs-literal">null</span></pre></div></div>
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</li>
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<li id="section-3">
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<div class="annotation">
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<div class="pilwrap ">
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<a class="pilcrow" href="#section-3">¶</a>
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</div>
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<p>Initialize a scope with its parent, for lookups up the chain,
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as well as a reference to the <strong>Block</strong> node it belongs to, which is
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where it should declare its variables, and a reference to the function that
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it belongs to.</p>
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</div>
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<div class="content"><div class='highlight'><pre> <span class="hljs-attribute">constructor</span>: <span class="hljs-function"><span class="hljs-params">(<span class="hljs-property">@parent</span>, <span class="hljs-property">@expressions</span>, <span class="hljs-property">@method</span>)</span> -></span>
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<span class="hljs-property">@variables</span> = [{<span class="hljs-attribute">name</span>: <span class="hljs-string">'arguments'</span>, <span class="hljs-attribute">type</span>: <span class="hljs-string">'arguments'</span>}]
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<span class="hljs-property">@positions</span> = {}
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Scope.root = <span class="hljs-keyword">this</span> <span class="hljs-keyword">unless</span> <span class="hljs-property">@parent</span></pre></div></div>
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</li>
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<li id="section-4">
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<div class="annotation">
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<div class="pilwrap ">
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<a class="pilcrow" href="#section-4">¶</a>
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</div>
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<p>Adds a new variable or overrides an existing one.</p>
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</div>
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<div class="content"><div class='highlight'><pre> <span class="hljs-attribute">add</span>: <span class="hljs-function"><span class="hljs-params">(name, type, immediate)</span> -></span>
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<span class="hljs-keyword">return</span> <span class="hljs-property">@parent</span>.add name, type, immediate <span class="hljs-keyword">if</span> <span class="hljs-property">@shared</span> <span class="hljs-keyword">and</span> <span class="hljs-keyword">not</span> immediate
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<span class="hljs-keyword">if</span> <span class="hljs-attribute">Object</span>::hasOwnProperty.call <span class="hljs-property">@positions</span>, name
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<span class="hljs-property">@variables</span>[<span class="hljs-property">@positions</span>[name]].type = type
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<span class="hljs-keyword">else</span>
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<span class="hljs-property">@positions</span>[name] = <span class="hljs-property">@variables</span>.push({name, type}) - <span class="hljs-number">1</span></pre></div></div>
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</li>
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<li id="section-5">
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<div class="annotation">
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<div class="pilwrap ">
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<a class="pilcrow" href="#section-5">¶</a>
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</div>
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<p>When <code>super</code> is called, we need to find the name of the current method we’re
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in, so that we know how to invoke the same method of the parent class. This
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can get complicated if super is being called from an inner function.
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<code>namedMethod</code> will walk up the scope tree until it either finds the first
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function object that has a name filled in, or bottoms out.</p>
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</div>
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<div class="content"><div class='highlight'><pre> <span class="hljs-attribute">namedMethod</span>:<span class="hljs-function"> -></span>
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<span class="hljs-keyword">return</span> <span class="hljs-property">@method</span> <span class="hljs-keyword">if</span> <span class="hljs-property">@method</span>?.name <span class="hljs-keyword">or</span> !<span class="hljs-property">@parent</span>
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<span class="hljs-property">@parent</span>.namedMethod()</pre></div></div>
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</li>
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<li id="section-6">
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<div class="annotation">
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<div class="pilwrap ">
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<a class="pilcrow" href="#section-6">¶</a>
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</div>
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<p>Look up a variable name in lexical scope, and declare it if it does not
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already exist.</p>
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</div>
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<div class="content"><div class='highlight'><pre> <span class="hljs-attribute">find</span>: <span class="hljs-function"><span class="hljs-params">(name)</span> -></span>
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<span class="hljs-keyword">return</span> <span class="hljs-literal">yes</span> <span class="hljs-keyword">if</span> <span class="hljs-property">@check</span> name
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<span class="hljs-property">@add</span> name, <span class="hljs-string">'var'</span>
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<span class="hljs-literal">no</span></pre></div></div>
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</li>
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<li id="section-7">
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<div class="annotation">
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<div class="pilwrap ">
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<a class="pilcrow" href="#section-7">¶</a>
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</div>
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<p>Reserve a variable name as originating from a function parameter for this
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scope. No <code>var</code> required for internal references.</p>
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</div>
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<div class="content"><div class='highlight'><pre> <span class="hljs-attribute">parameter</span>: <span class="hljs-function"><span class="hljs-params">(name)</span> -></span>
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<span class="hljs-keyword">return</span> <span class="hljs-keyword">if</span> <span class="hljs-property">@shared</span> <span class="hljs-keyword">and</span> <span class="hljs-property">@parent</span>.check name, <span class="hljs-literal">yes</span>
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<span class="hljs-property">@add</span> name, <span class="hljs-string">'param'</span></pre></div></div>
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</li>
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<li id="section-8">
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<div class="annotation">
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<div class="pilwrap ">
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<a class="pilcrow" href="#section-8">¶</a>
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</div>
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<p>Just check to see if a variable has already been declared, without reserving,
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walks up to the root scope.</p>
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</div>
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<div class="content"><div class='highlight'><pre> <span class="hljs-attribute">check</span>: <span class="hljs-function"><span class="hljs-params">(name)</span> -></span>
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!!(<span class="hljs-property">@type</span>(name) <span class="hljs-keyword">or</span> <span class="hljs-property">@parent</span>?.check(name))</pre></div></div>
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</li>
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<li id="section-9">
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<div class="annotation">
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<div class="pilwrap ">
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<a class="pilcrow" href="#section-9">¶</a>
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</div>
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<p>Generate a temporary variable name at the given index.</p>
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</div>
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<div class="content"><div class='highlight'><pre> <span class="hljs-attribute">temporary</span>: <span class="hljs-function"><span class="hljs-params">(name, index)</span> -></span>
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<span class="hljs-keyword">if</span> name.length > <span class="hljs-number">1</span>
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<span class="hljs-string">'_'</span> + name + <span class="hljs-keyword">if</span> index > <span class="hljs-number">1</span> <span class="hljs-keyword">then</span> index - <span class="hljs-number">1</span> <span class="hljs-keyword">else</span> <span class="hljs-string">''</span>
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<span class="hljs-keyword">else</span>
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<span class="hljs-string">'_'</span> + (index + parseInt name, <span class="hljs-number">36</span>).toString(<span class="hljs-number">36</span>).replace <span class="hljs-regexp">/\d/g</span>, <span class="hljs-string">'a'</span></pre></div></div>
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</li>
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<li id="section-10">
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<div class="annotation">
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<div class="pilwrap ">
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<a class="pilcrow" href="#section-10">¶</a>
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</div>
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<p>Gets the type of a variable.</p>
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</div>
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<div class="content"><div class='highlight'><pre> <span class="hljs-attribute">type</span>: <span class="hljs-function"><span class="hljs-params">(name)</span> -></span>
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<span class="hljs-keyword">return</span> v.type <span class="hljs-keyword">for</span> v <span class="hljs-keyword">in</span> <span class="hljs-property">@variables</span> <span class="hljs-keyword">when</span> v.name <span class="hljs-keyword">is</span> name
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<span class="hljs-literal">null</span></pre></div></div>
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</li>
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<li id="section-11">
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<div class="annotation">
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<div class="pilwrap ">
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<a class="pilcrow" href="#section-11">¶</a>
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</div>
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<p>If we need to store an intermediate result, find an available name for a
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compiler-generated variable. <code>_var</code>, <code>_var2</code>, and so on…</p>
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</div>
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<div class="content"><div class='highlight'><pre> <span class="hljs-attribute">freeVariable</span>: <span class="hljs-function"><span class="hljs-params">(name, reserve=<span class="hljs-literal">true</span>)</span> -></span>
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index = <span class="hljs-number">0</span>
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index++ <span class="hljs-keyword">while</span> <span class="hljs-property">@check</span>((temp = <span class="hljs-property">@temporary</span> name, index))
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<span class="hljs-property">@add</span> temp, <span class="hljs-string">'var'</span>, <span class="hljs-literal">yes</span> <span class="hljs-keyword">if</span> reserve
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temp</pre></div></div>
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</li>
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<li id="section-12">
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<div class="annotation">
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<div class="pilwrap ">
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<a class="pilcrow" href="#section-12">¶</a>
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</div>
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<p>Ensure that an assignment is made at the top of this scope
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(or at the top-level scope, if requested).</p>
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</div>
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<div class="content"><div class='highlight'><pre> <span class="hljs-attribute">assign</span>: <span class="hljs-function"><span class="hljs-params">(name, value)</span> -></span>
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<span class="hljs-property">@add</span> name, {value, <span class="hljs-attribute">assigned</span>: <span class="hljs-literal">yes</span>}, <span class="hljs-literal">yes</span>
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<span class="hljs-property">@hasAssignments</span> = <span class="hljs-literal">yes</span></pre></div></div>
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</li>
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<li id="section-13">
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<div class="annotation">
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<div class="pilwrap ">
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<a class="pilcrow" href="#section-13">¶</a>
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</div>
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<p>Does this scope have any declared variables?</p>
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</div>
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<div class="content"><div class='highlight'><pre> <span class="hljs-attribute">hasDeclarations</span>:<span class="hljs-function"> -></span>
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!!<span class="hljs-property">@declaredVariables</span>().length</pre></div></div>
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</li>
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<li id="section-14">
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<div class="annotation">
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<div class="pilwrap ">
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<a class="pilcrow" href="#section-14">¶</a>
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</div>
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<p>Return the list of variables first declared in this scope.</p>
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</div>
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<div class="content"><div class='highlight'><pre> <span class="hljs-attribute">declaredVariables</span>:<span class="hljs-function"> -></span>
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realVars = []
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tempVars = []
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<span class="hljs-keyword">for</span> v <span class="hljs-keyword">in</span> <span class="hljs-property">@variables</span> <span class="hljs-keyword">when</span> v.type <span class="hljs-keyword">is</span> <span class="hljs-string">'var'</span>
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(<span class="hljs-keyword">if</span> v.name.charAt(<span class="hljs-number">0</span>) <span class="hljs-keyword">is</span> <span class="hljs-string">'_'</span> <span class="hljs-keyword">then</span> tempVars <span class="hljs-keyword">else</span> realVars).push v.name
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realVars.sort().concat tempVars.sort()</pre></div></div>
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</li>
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<li id="section-15">
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<div class="annotation">
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<div class="pilwrap ">
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<a class="pilcrow" href="#section-15">¶</a>
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</div>
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<p>Return the list of assignments that are supposed to be made at the top
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of this scope.</p>
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</div>
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<div class="content"><div class='highlight'><pre> <span class="hljs-attribute">assignedVariables</span>:<span class="hljs-function"> -></span>
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<span class="hljs-string">"<span class="hljs-subst">#{v.name}</span> = <span class="hljs-subst">#{v.type.value}</span>"</span> <span class="hljs-keyword">for</span> v <span class="hljs-keyword">in</span> <span class="hljs-property">@variables</span> <span class="hljs-keyword">when</span> v.type.assigned</pre></div></div>
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</li>
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</ul>
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</div>
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</body>
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</html>
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