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Expression evaluation

This article explains how expressions are evaluated in XC=BASIC.

Expression

<html> <svg xmlns=“http://www.w3.org/2000/svg” width=“175” height=“169”> 

       <defs>
          <style type="text/css">
  @namespace "http://www.w3.org/2000/svg";
  .line                 {fill: none; stroke: #332900;}
  .bold-line            {stroke: #141000; shape-rendering: crispEdges; stroke-width: 2; }
  .thin-line            {stroke: #1F1800; shape-rendering: crispEdges}
  .filled               {fill: #332900; stroke: none;}
  text.terminal         {font-family: Verdana, Sans-serif;
                          font-size: 12px;
                          fill: #141000;
                          font-weight: bold;
                        }
  text.nonterminal      {font-family: Verdana, Sans-serif;
                          font-size: 12px;
                          fill: #1A1400;
                          font-weight: normal;
                        }
  text.regexp           {font-family: Verdana, Sans-serif;
                          font-size: 12px;
                          fill: #1F1800;
                          font-weight: normal;
                        }
  rect, circle, polygon {fill: #332900; stroke: #332900;}
  rect.terminal         {fill: #FFDB4D; stroke: #332900;}
  rect.nonterminal      {fill: #FFEC9E; stroke: #332900;}
  rect.text             {fill: none; stroke: none;}    
  polygon.regexp        {fill: #FFF4C7; stroke: #332900;}
</style>
       </defs>
       <polygon points="9 149 1 145 1 153"/>
       <polygon points="17 149 9 145 9 153"/><a xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="#Simplexp" xlink:title="Simplexp">
          <rect x="51" y="135" width="76" height="32"/>
          <rect x="49" y="133" width="76" height="32" class="nonterminal"/>
          <text class="nonterminal" x="59" y="153">Simplexp</text></a><rect x="51" y="91" width="30" height="32" rx="10"/>
       <rect x="49" y="89" width="30" height="32" class="terminal" rx="10"/>
       <text class="terminal" x="59" y="109">&amp;</text>
       <rect x="51" y="47" width="26" height="32" rx="10"/>
       <rect x="49" y="45" width="26" height="32" class="terminal" rx="10"/>
       <text class="terminal" x="59" y="65">|</text>
       <rect x="51" y="3" width="30" height="32" rx="10"/>
       <rect x="49" y="1" width="30" height="32" class="terminal" rx="10"/>
       <text class="terminal" x="59" y="21">^</text>
       <path xmlns:svg="http://www.w3.org/2000/svg" class="line" d="m17 149 h2 m20 0 h10 m76 0 h10 m-116 0 l20 0 m-1 0 q-9 0 -9 -10 l0 -24 q0 -10 10 -10 m96 44 l20 0 m-20 0 q10 0 10 -10 l0 -24 q0 -10 -10 -10 m-96 0 h10 m30 0 h10 m0 0 h46 m-106 10 l0 -44 q0 -10 10 -10 m106 54 l0 -44 q0 -10 -10 -10 m-96 0 h10 m26 0 h10 m0 0 h50 m-106 10 l0 -44 q0 -10 10 -10 m106 54 l0 -44 q0 -10 -10 -10 m-96 0 h10 m30 0 h10 m0 0 h46 m23 132 h-3"/>
       <polygon points="165 149 173 145 173 153"/>
       <polygon points="165 149 157 145 157 153"/></svg>

</html>