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<title>Debugging with GDB: M2 Operators</title>
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<a name="M2-Operators"></a>
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<p>
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Next: <a href="Built_002dIn-Func_002fProc.html#Built_002dIn-Func_002fProc" accesskey="n" rel="next">Built-In Func/Proc</a>, Up: <a href="Modula_002d2.html#Modula_002d2" accesskey="u" rel="up">Modula-2</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html#Concept-Index" title="Index" rel="index">Index</a>]</p>
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<hr>
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<a name="Operators"></a>
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<h4 class="subsubsection">15.4.9.1 Operators</h4>
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<a name="index-Modula_002d2-operators"></a>
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<p>Operators must be defined on values of specific types. For instance,
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<code>+</code> is defined on numbers, but not on structures. Operators are
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often defined on groups of types. For the purposes of Modula-2, the
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following definitions hold:
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</p>
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<ul>
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<li> <em>Integral types</em> consist of <code>INTEGER</code>, <code>CARDINAL</code>, and
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their subranges.
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</li><li> <em>Character types</em> consist of <code>CHAR</code> and its subranges.
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</li><li> <em>Floating-point types</em> consist of <code>REAL</code>.
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</li><li> <em>Pointer types</em> consist of anything declared as <code>POINTER TO
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<var>type</var></code>.
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</li><li> <em>Scalar types</em> consist of all of the above.
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</li><li> <em>Set types</em> consist of <code>SET</code> and <code>BITSET</code> types.
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</li><li> <em>Boolean types</em> consist of <code>BOOLEAN</code>.
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</li></ul>
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<p>The following operators are supported, and appear in order of
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increasing precedence:
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</p>
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<dl compact="compact">
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<dt><code>,</code></dt>
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<dd><p>Function argument or array index separator.
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</p>
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</dd>
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<dt><code>:=</code></dt>
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<dd><p>Assignment. The value of <var>var</var> <code>:=</code> <var>value</var> is
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<var>value</var>.
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</p>
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</dd>
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<dt><code><<span class="roman">, </span>></code></dt>
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<dd><p>Less than, greater than on integral, floating-point, or enumerated
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types.
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</p>
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</dd>
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<dt><code><=<span class="roman">, </span>>=</code></dt>
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<dd><p>Less than or equal to, greater than or equal to
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on integral, floating-point and enumerated types, or set inclusion on
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set types. Same precedence as <code><</code>.
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</p>
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</dd>
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<dt><code>=<span class="roman">, </span><><span class="roman">, </span>#</code></dt>
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<dd><p>Equality and two ways of expressing inequality, valid on scalar types.
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Same precedence as <code><</code>. In <small>GDB</small> scripts, only <code><></code> is
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available for inequality, since <code>#</code> conflicts with the script
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comment character.
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</p>
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</dd>
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<dt><code>IN</code></dt>
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<dd><p>Set membership. Defined on set types and the types of their members.
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Same precedence as <code><</code>.
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</p>
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</dd>
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<dt><code>OR</code></dt>
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<dd><p>Boolean disjunction. Defined on boolean types.
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</p>
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</dd>
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<dt><code>AND<span class="roman">, </span>&</code></dt>
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<dd><p>Boolean conjunction. Defined on boolean types.
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</p>
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</dd>
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<dt><code>@</code></dt>
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<dd><p>The <small>GDB</small> “artificial array” operator (see <a href="Expressions.html#Expressions">Expressions</a>).
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</p>
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</dd>
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<dt><code>+<span class="roman">, </span>-</code></dt>
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<dd><p>Addition and subtraction on integral and floating-point types, or union
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and difference on set types.
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</p>
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</dd>
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<dt><code>*</code></dt>
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<dd><p>Multiplication on integral and floating-point types, or set intersection
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on set types.
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</p>
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</dd>
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<dt><code>/</code></dt>
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<dd><p>Division on floating-point types, or symmetric set difference on set
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types. Same precedence as <code>*</code>.
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</p>
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</dd>
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<dt><code>DIV<span class="roman">, </span>MOD</code></dt>
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<dd><p>Integer division and remainder. Defined on integral types. Same
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precedence as <code>*</code>.
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</p>
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</dd>
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<dt><code>-</code></dt>
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<dd><p>Negative. Defined on <code>INTEGER</code> and <code>REAL</code> data.
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</p>
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</dd>
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<dt><code>^</code></dt>
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<dd><p>Pointer dereferencing. Defined on pointer types.
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</p>
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</dd>
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<dt><code>NOT</code></dt>
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<dd><p>Boolean negation. Defined on boolean types. Same precedence as
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<code>^</code>.
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</p>
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</dd>
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<dt><code>.</code></dt>
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<dd><p><code>RECORD</code> field selector. Defined on <code>RECORD</code> data. Same
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precedence as <code>^</code>.
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</p>
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</dd>
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<dt><code>[]</code></dt>
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<dd><p>Array indexing. Defined on <code>ARRAY</code> data. Same precedence as <code>^</code>.
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</p>
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</dd>
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<dt><code>()</code></dt>
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<dd><p>Procedure argument list. Defined on <code>PROCEDURE</code> objects. Same precedence
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as <code>^</code>.
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</p>
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</dd>
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<dt><code>::<span class="roman">, </span>.</code></dt>
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<dd><p><small>GDB</small> and Modula-2 scope operators.
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</p></dd>
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</dl>
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<blockquote>
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<p><em>Warning:</em> Set expressions and their operations are not yet supported, so <small>GDB</small>
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treats the use of the operator <code>IN</code>, or the use of operators
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<code>+</code>, <code>-</code>, <code>*</code>, <code>/</code>, <code>=</code>, , <code><></code>, <code>#</code>,
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<code><=</code>, and <code>>=</code> on sets as an error.
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</p></blockquote>
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Next: <a href="Built_002dIn-Func_002fProc.html#Built_002dIn-Func_002fProc" accesskey="n" rel="next">Built-In Func/Proc</a>, Up: <a href="Modula_002d2.html#Modula_002d2" accesskey="u" rel="up">Modula-2</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html#Concept-Index" title="Index" rel="index">Index</a>]</p>
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