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  <div class="section" id="eval-and-debugging">
<h1>Eval() and Debugging<a class="headerlink" href="#eval-and-debugging" title="Permalink to this headline">¶</a></h1>
<p id="index-0">In this chapter we are going to learn about</p>
<ul class="simple">
<li>Error Handling using Try/Catch/Done</li>
<li>Eval() function</li>
<li>Raise() function</li>
<li>Assert() function</li>
</ul>
<div class="section" id="try-catch-done">
<span id="index-1"></span><h2>Try/Catch/Done<a class="headerlink" href="#try-catch-done" title="Permalink to this headline">¶</a></h2>
<p>Syntax:</p>
<div class="highlight-none"><div class="highlight"><pre>Try
        Statements...
Catch
        Statements...
Done
</pre></div>
</div>
<p>The statements in the Try block will be executed, if any error happens then
the statements in the catch block will be executed.</p>
<p>Inside the catch block we can use the variable cCatchError to get the error message</p>
<p>Example:</p>
<div class="highlight-none"><div class="highlight"><pre>Try
        see 5/0
Catch
        see &quot;Catch!&quot; + nl + cCatchError
Done
</pre></div>
</div>
<p>Output:</p>
<div class="highlight-none"><div class="highlight"><pre>Catch!
Error (R1) : Cann&#39;t divide by zero !
</pre></div>
</div>
</div>
<div class="section" id="eval-function">
<span id="index-2"></span><h2>Eval() Function<a class="headerlink" href="#eval-function" title="Permalink to this headline">¶</a></h2>
<p>We can execute code during the runtime from string using the Eval() function</p>
<p>Syntax:</p>
<div class="highlight-none"><div class="highlight"><pre>Eval(cCode)
</pre></div>
</div>
<p>Example:</p>
<div class="highlight-none"><div class="highlight"><pre>Eval(&quot;nOutput = 5+2*5 &quot; )
See &quot;5+2*5 = &quot; + nOutput + nl
Eval(&quot;for x = 1 to 10 see x + nl next&quot;)
Eval(&quot;func test see &#39;message from test!&#39; &quot;)
test()
</pre></div>
</div>
<p>Output:</p>
<div class="highlight-none"><div class="highlight"><pre>5+2*5 = 15
1
2
3
4
5
6
7
8
9
10
message from test!
</pre></div>
</div>
</div>
<div class="section" id="raise-function">
<span id="index-3"></span><h2>Raise() Function<a class="headerlink" href="#raise-function" title="Permalink to this headline">¶</a></h2>
<p>We can raise an exception using the Raise() function</p>
<p>Syntax:</p>
<div class="highlight-none"><div class="highlight"><pre>Raise(cErrorMessage)
</pre></div>
</div>
<p>The function will display the error message then end the execution of the program.</p>
<p>We can use Try/Catch/Done to avoid exceptions generated by raise() function.</p>
<p>Example:</p>
<div class="highlight-none"><div class="highlight"><pre>nMode = 10

if nMode &lt; 0 or nMode &gt; 5
        raise(&quot;Error : nMode not in the range 1:4&quot;)
ok
</pre></div>
</div>
<p>Output:</p>
<div class="highlight-none"><div class="highlight"><pre>Line 4 Error : nMode not in the range 1:4
In raise in file tests\raise.ring
</pre></div>
</div>
<p>Example:</p>
<div class="highlight-none"><div class="highlight"><pre>try
        testmode(6)
catch
        see &quot;avoid raise!&quot;
done

testmode(-1)

func testmode nMode

        if nMode &lt; 0 or nMode &gt; 5
                raise(&quot;Error : nMode not in the range 1:4&quot;)
        ok
</pre></div>
</div>
<p>Output:</p>
<div class="highlight-none"><div class="highlight"><pre>avoid raise!
Line 12 Error : nMode not in the range 1:4
In raise In function testmode() in file tests\raise2.ring
called from line 7  in file tests\raise2.ring
</pre></div>
</div>
</div>
<div class="section" id="assert-function">
<span id="index-4"></span><h2>Assert() Function<a class="headerlink" href="#assert-function" title="Permalink to this headline">¶</a></h2>
<p>We can use the Assert() function to test conditions before executing the code</p>
<p>If the test fail the program will be terminated with an error message contains the assert condition.</p>
<p>Syntax:</p>
<div class="highlight-none"><div class="highlight"><pre>Assert( condition )
</pre></div>
</div>
<p>Example:</p>
<div class="highlight-none"><div class="highlight"><pre>x = 10
assert( x = 10)
assert( x = 100 )
</pre></div>
</div>
<p>Output:</p>
<div class="highlight-none"><div class="highlight"><pre>Line 3 Assertion Failed!
In assert in file tests\assert.ring
</pre></div>
</div>
</div>
</div>


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  <h3><a href="index.html">Table Of Contents</a></h3>
  <ul>
<li><a class="reference internal" href="#">Eval() and Debugging</a><ul>
<li><a class="reference internal" href="#try-catch-done">Try/Catch/Done</a></li>
<li><a class="reference internal" href="#eval-function">Eval() Function</a></li>
<li><a class="reference internal" href="#raise-function">Raise() Function</a></li>
<li><a class="reference internal" href="#assert-function">Assert() Function</a></li>
</ul>
</li>
</ul>

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