142 lines
6.3 KiB
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142 lines
6.3 KiB
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<title>M2 Operators - Debugging with GDB</title>
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<link rel="up" href="Modula_002d2.html#Modula_002d2" title="Modula-2">
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<link rel="next" href="Built_002dIn-Func_002fProc.html#Built_002dIn-Func_002fProc" title="Built-In Func/Proc">
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<body>
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<div class="node">
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<a name="M2-Operators"></a>
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<p>
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Next: <a rel="next" accesskey="n" href="Built_002dIn-Func_002fProc.html#Built_002dIn-Func_002fProc">Built-In Func/Proc</a>,
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Up: <a rel="up" accesskey="u" href="Modula_002d2.html#Modula_002d2">Modula-2</a>
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<hr>
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</div>
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<h5 class="subsubsection">15.4.9.1 Operators</h5>
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<p><a name="index-Modula_002d2-operators-1044"></a>
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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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<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><em>Character types</em> consist of <code>CHAR</code> and its subranges.
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<li><em>Floating-point types</em> consist of <code>REAL</code>.
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<li><em>Pointer types</em> consist of anything declared as <code>POINTER TO
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</code><var>type</var>.
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<li><em>Scalar types</em> consist of all of the above.
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<li><em>Set types</em> consist of <code>SET</code> and <code>BITSET</code> types.
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<li><em>Boolean types</em> consist of <code>BOOLEAN</code>.
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</ul>
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<p class="noindent">The following operators are supported, and appear in order of
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increasing precedence:
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<dl>
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<dt><code>,</code><dd>Function argument or array index separator.
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<br><dt><code>:=</code><dd>Assignment. The value of <var>var</var> <code>:=</code> <var>value</var> is
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<var>value</var>.
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<br><dt><code><</code><span class="roman">, </span><code>></code><dd>Less than, greater than on integral, floating-point, or enumerated
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types.
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<br><dt><code><=</code><span class="roman">, </span><code>>=</code><dd>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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<br><dt><code>=</code><span class="roman">, </span><code><></code><span class="roman">, </span><code>#</code><dd>Equality and two ways of expressing inequality, valid on scalar types.
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Same precedence as <code><</code>. In <span class="sc">gdb</span> 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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<br><dt><code>IN</code><dd>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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<br><dt><code>OR</code><dd>Boolean disjunction. Defined on boolean types.
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<br><dt><code>AND</code><span class="roman">, </span><code>&</code><dd>Boolean conjunction. Defined on boolean types.
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<br><dt><code>@</code><dd>The <span class="sc">gdb</span> “artificial array” operator (see <a href="Expressions.html#Expressions">Expressions</a>).
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<br><dt><code>+</code><span class="roman">, </span><code>-</code><dd>Addition and subtraction on integral and floating-point types, or union
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and difference on set types.
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<br><dt><code>*</code><dd>Multiplication on integral and floating-point types, or set intersection
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on set types.
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<br><dt><code>/</code><dd>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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<br><dt><code>DIV</code><span class="roman">, </span><code>MOD</code><dd>Integer division and remainder. Defined on integral types. Same
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precedence as <code>*</code>.
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<br><dt><code>-</code><dd>Negative. Defined on <code>INTEGER</code> and <code>REAL</code> data.
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<br><dt><code>^</code><dd>Pointer dereferencing. Defined on pointer types.
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<br><dt><code>NOT</code><dd>Boolean negation. Defined on boolean types. Same precedence as
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<code>^</code>.
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<br><dt><code>.</code><dd><code>RECORD</code> field selector. Defined on <code>RECORD</code> data. Same
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precedence as <code>^</code>.
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<br><dt><code>[]</code><dd>Array indexing. Defined on <code>ARRAY</code> data. Same precedence as <code>^</code>.
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<br><dt><code>()</code><dd>Procedure argument list. Defined on <code>PROCEDURE</code> objects. Same precedence
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as <code>^</code>.
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<br><dt><code>::</code><span class="roman">, </span><code>.</code><dd><span class="sc">gdb</span> and Modula-2 scope operators.
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</dl>
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<blockquote>
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<em>Warning:</em> Set expressions and their operations are not yet supported, so <span class="sc">gdb</span>
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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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</blockquote>
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</body></html>
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