nils
/
WhileInterpreter
mirror of https://github.com/malteschmitz/WhileInterpreter.git
1
0
Fork 0
Code Issues 0 Releases 0 Wiki Activity
You can not select more than 25 topics Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
4 Commits
4 Branches
3.2 MiB
 
Tree: 6eb4c44924
Branches Tags
${ item.name }
Create branch ${ searchTerm }
from '6eb4c44924'
${ noResults }
WhileInterpreter/docco/vertical/src/main/java/interpreter/Evaluator.java.html

48 lines
10 KiB
Raw Blame History 

  1. <!DOCTYPE html><html><head><meta http-equiv="content-type" content="text/html;charset=utf-8"><title>Evaluator.java</title><link href="../../../../css/bootstrap.min.css" rel="stylesheet" type="text/css"/><link href="../../../../css/bootstrap-responsive.min.css" rel="stylesheet" type="text/css"/><link href="../../../../css/atlassian-docco.css" rel="stylesheet" type="text/css"/><link rel="stylesheet" class="codebrush light" title="IDEA" href="//yandex.st/highlightjs/6.2/styles/idea.min.css"/><link rel="alternate stylesheet" class="codebrush light" title="Google Code" href="//yandex.st/highlightjs/6.2/styles/googlecode.min.css"/><link rel="alternate stylesheet" class="codebrush light" title="GitHub" href="//yandex.st/highlightjs/6.2/styles/github.min.css"/><link rel="alternate stylesheet" class="codebrush light" title="Visual Studio" href="//yandex.st/highlightjs/6.2/styles/vs.min.css"/><link rel="alternate stylesheet" class="codebrush light" title="Magula" href="//yandex.st/highlightjs/6.2/styles/magula.min.css"/><link rel="alternate stylesheet" class="codebrush dark" title="Zenburn" href="//yandex.st/highlightjs/6.2/styles/zenburn.min.css"/><link rel="alternate stylesheet" class="codebrush dark" title="Arta" href="//yandex.st/highlightjs/6.2/styles/arta.min.css"/><link rel="alternate stylesheet" class="codebrush dark" title="Monokai" href="//yandex.st/highlightjs/6.2/styles/monokai.min.css"/><link rel="alternate stylesheet" class="codebrush dark" title="IR Black" href="//yandex.st/highlightjs/6.2/styles/ir_black.min.css"/><link rel="alternate stylesheet" class="codebrush dark" title="Solarized Dark" href="//yandex.st/highlightjs/6.2/styles/solarized_dark.min.css"/><script type="text/javascript" src="//ajax.googleapis.com/ajax/libs/jquery/1.7.2/jquery.min.js"></script><script type="text/javascript" src="//yandex.st/highlightjs/6.2/highlight.min.js"></script><script type="text/javascript" src="../../../../js/jquery.cookie.js"></script><script type="text/javascript" src="../../../../js/bootstrap.min.js"></script><script type="text/javascript" src="../../../../js/atlassian-docco.js"></script></head><body><div class="navbar navbar-fixed-top"><div class="navbar-inner"><div class="container-fluid"><a class="btn btn-navbar" data-toggle="collapse" data-target=".nav-collapse"><span class="icon-bar"></span><span class="icon-bar"></span><span class="icon-bar"></span></a><a class="brand" href="#">Evaluator.java</a><div class="nav-collapse"><ul class="nav"><li class="dropdown"><a href="#" class="dropdown-toggle" data-toggle="dropdown">Index <b class="caret"></b></a><ul class="dropdown-menu"><li class="nav-header">Expression</li><li><a href="../../../../src/main/java/expression/Addition.java.html">Addition.java</a></li><li><a href="../../../../src/main/java/expression/Expression.java.html">Expression.java</a></li><li><a href="../../../../src/main/java/expression/Identifier.java.html">Identifier.java</a></li><li><a href="../../../../src/main/java/expression/Int.java.html">Int.java</a></li><li><a href="../../../../src/main/java/expression/Subtraction.java.html">Subtraction.java</a></li><li class="nav-header">Interpreter</li><li class="active"><a href="../../../../src/main/java/interpreter/Evaluator.java.html">Evaluator.java</a></li><li><a href="../../../../src/main/java/interpreter/Interpreter.java.html">Interpreter.java</a></li><li><a href="../../../../src/main/java/interpreter/InterpreterException.java.html">InterpreterException.java</a></li><li><a href="../../../../src/main/java/interpreter/Visitor.java.html">Visitor.java</a></li><li class="nav-header">Parser</li><li><a href="../../../../src/main/java/parser/Parser.java.html">Parser.java</a></li><li><a href="../../../../src/main/java/parser/SyntaxException.java.html">SyntaxException.java</a></li><li class="nav-header">Printer</li><li><a href="../../../../src/main/java/printer/ExpressionPrinter.java.html">ExpressionPrinter.java</a></li><li><a href="../../../../src/main/java/printer/ProgramPrinter.java.html">ProgramPrinter.java</a></li><li class="nav-header">Program</li><li><a href="../../../../src/main/java/program/Assignment.java.html">Assignment.java</a></li><li><a href="../../../../src/main/java/program/Composition.java.html">Composition.java</a></li><li><a href="../../../../src/main/java/program/Conditional.java.html">Conditional.java</a></li><li><a href="../../../../src/main/java/program/Loop.java.html">Loop.java</a></li><li><a href="../../../../src/main/java/program/Program.java.html">Program.java</a></li></ul></li><li class="dropdown"><a href="#" class="dropdown-toggle" data-toggle="dropdown">Theme <b class="caret"></b></a><ul id="themeDropdown" class="dropdown-menu"></ul></li><li class="dropdown"><a href="#" class="dropdown-toggle" data-toggle="dropdown">Layout <b class="caret"></b></a><ul class="dropdown-menu"><li><a href="../../../../../horizontal/src/main/java/interpreter/Evaluator.java.html">Horizontal</a></li><li class="active"><a href="#">Vertical</a></li></ul></li></ul></div><!--/.nav-collapse --></div></div></div><div class="container-fluid docco-container"><div class="row-fluid"><div class="span12"><h1>Evaluator</h1><p>The evaluator implements the semantics defined by the function <code>eval: Expr * V -&gt; Z</code>, where <code>V = Id -&gt; Z</code> is the set of all variable valuations to the set <code>Z</code> set of integers. <code>eval</code> is inductively defined as follows:</p>

  2. <pre><code>eval(e1 &quot;+&quot; e2, v) = eval(e1, v) + eval(e2, v)

  3. eval(e1 &quot;-&quot; e2, v) = eval(e1, v) − eval(e2, v)

  4. eval(x, v) = v(x)

  5. eval(z, v) = z

  6. </code></pre><p>with</p>

  7. <ul>

  8.   <li>expressions <code>e</code>, <code>e1</code>, <code>e2</code>,</li>

  9.   <li>a variable valuation <code>v</code>,</li>

  10.   <li>and identifier <code>x</code> and</li>

  11.   <li>an integer <code>z</code>.</li>

  12. </ul></div></div><div id="section-0" class="docco-section"><div class="row-fluid"><div class="span12 doc"><span class="label label-info"><a style="color:white" href="#section-0">0</a></span><div class="doctext hidden-doc"></div></div></div><div class="row-fluid"><div class="span12 code"><div class="hidden-code-line">------------------<a href="javascript:void(0)" class="hidden-code-toggle" index="0">Show  Header  Code (<span class="linecount"></span> lines)</a>------------------</div><pre class="hidden-code"><code class="java">package interpreter;

  13. 

  14. import expression.*;

  15. 

  16. import java.util.HashMap;

  17. import java.util.Map;</code></pre></div></div></div><div id="section-1" class="docco-section"><div class="row-fluid"><div class="span12 doc"><span class="label label-info"><a style="color:white" href="#section-1">1</a></span><div class="doctext"><p>The <code>Evaluator</code> implements the evaluation function defined above with the help of the <a href="../../../../src/main/java/interpreter/Visitor.java.html">Visitor</a>. The <code>Evaluator</code> takes an <code>Expression</code> in the constructor and provides a method <code>eval()</code> which evaluates the given expression and returns the result as an integer. For a given <code>expression</code> of type <code>Expression</code> it can be used as follows</p>

  18. <pre><code>Evaluator evaluator = new Evaluator(expression, valuation)

  19. System.out.println(evaluator.getValue());

  20. </code></pre><p>The evaluation function <code>eval</code> takes the variable valuation <code>v</code>, which is passed on recursively. As the valuation is not changed during the evaluation process, it can be stored in a global variable which is not changed. </p></div></div></div><div class="row-fluid"><div class="span12 code"><pre><code class="java">public class Evaluator extends Visitor&lt;Integer&gt; {

  21.     private final int value;

  22.     private final Map&lt;String, Integer&gt; valuation = new HashMap&lt;String, Integer&gt;();

  23. 

  24.     public Evaluator(Expression expression, Map&lt;String, Integer&gt; valuation) {

  25.         this.valuation.putAll(valuation);

  26.         value = visit(expression);

  27.     }

  28. 

  29.     public int getValue() {

  30.         return value;

  31.     }</code></pre></div></div></div><div id="section-2" class="docco-section"><div class="row-fluid"><div class="span12 doc"><span class="label label-info"><a style="color:white" href="#section-2">2</a></span><div class="doctext"><pre><code>eval(e1 &quot;+&quot; e2, v) = eval(e1, v) + eval(e2, v)

  32. </code></pre></div></div></div><div class="row-fluid"><div class="span12 code"><pre><code class="java">    public Integer visitAddition(Addition addition) {

  33.         return visit(addition.leftHandSide) + visit(addition.rightHandSide);

  34.     }</code></pre></div></div></div><div id="section-3" class="docco-section"><div class="row-fluid"><div class="span12 doc"><span class="label label-info"><a style="color:white" href="#section-3">3</a></span><div class="doctext"><pre><code>eval(e1 &quot;-&quot; e2, v) = eval(e1, v) - eval(e2, v)

  35. </code></pre></div></div></div><div class="row-fluid"><div class="span12 code"><pre><code class="java">    public Integer visitSubtraction(Subtraction subtraction) {

  36.         return visit(subtraction.leftHandSide) - visit(subtraction.rightHandSide);

  37.     }</code></pre></div></div></div><div id="section-4" class="docco-section"><div class="row-fluid"><div class="span12 doc"><span class="label label-info"><a style="color:white" href="#section-4">4</a></span><div class="doctext"><pre><code>eval(x, v) = v(x)

  38. </code></pre></div></div></div><div class="row-fluid"><div class="span12 code"><pre><code class="java">    public Integer visitInt(Int integer) {

  39.         return integer.value;

  40.     }

  41. 

  42.     public Integer visitIdentifier(Identifier identifier) {</code></pre></div></div></div><div id="section-5" class="docco-section"><div class="row-fluid"><div class="span12 doc"><span class="label label-info"><a style="color:white" href="#section-5">5</a></span><div class="doctext"><p>Make sure that the identifier actually exists in the valuation and raise an exception otherwise. </p></div></div></div><div class="row-fluid"><div class="span12 code"><pre><code class="java">        if (valuation.containsKey(identifier.name)) {</code></pre></div></div></div><div id="section-6" class="docco-section"><div class="row-fluid"><div class="span12 doc"><span class="label label-info"><a style="color:white" href="#section-6">6</a></span><div class="doctext"><pre><code>eval(z, v) = z

  43. </code></pre></div></div></div><div class="row-fluid"><div class="span12 code"><pre><code class="java">            return valuation.get(identifier.name);

  44.         } else {

  45.             throw new InterpreterException(&quot;Identifier &quot; + identifier.name + &quot; not found.&quot;);

  46.         }

  47.     }

  48. }</code></pre></div></div></div></div></body></html>