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| <h5 class="subsubsection">15.4.6.1 Operators</h5> |
| |
| <p><a name="index-Modula_002d2-operators-846"></a> |
| Operators must be defined on values of specific types. For instance, |
| <code>+</code> is defined on numbers, but not on structures. Operators are |
| often defined on groups of types. For the purposes of Modula-2, the |
| following definitions hold: |
| |
| <ul> |
| <li><em>Integral types</em> consist of <code>INTEGER</code>, <code>CARDINAL</code>, and |
| their subranges. |
| |
| <li><em>Character types</em> consist of <code>CHAR</code> and its subranges. |
| |
| <li><em>Floating-point types</em> consist of <code>REAL</code>. |
| |
| <li><em>Pointer types</em> consist of anything declared as <code>POINTER TO |
| </code><var>type</var>. |
| |
| <li><em>Scalar types</em> consist of all of the above. |
| |
| <li><em>Set types</em> consist of <code>SET</code> and <code>BITSET</code> types. |
| |
| <li><em>Boolean types</em> consist of <code>BOOLEAN</code>. |
| </ul> |
| |
| <p class="noindent">The following operators are supported, and appear in order of |
| increasing precedence: |
| |
| <dl> |
| <dt><code>,</code><dd>Function argument or array index separator. |
| |
| <br><dt><code>:=</code><dd>Assignment. The value of <var>var</var> <code>:=</code> <var>value</var> is |
| <var>value</var>. |
| |
| <br><dt><code><</code><span class="roman">, </span><code>></code><dd>Less than, greater than on integral, floating-point, or enumerated |
| types. |
| |
| <br><dt><code><=</code><span class="roman">, </span><code>>=</code><dd>Less than or equal to, greater than or equal to |
| on integral, floating-point and enumerated types, or set inclusion on |
| set types. Same precedence as <code><</code>. |
| |
| <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. |
| Same precedence as <code><</code>. In <span class="sc">gdb</span> scripts, only <code><></code> is |
| available for inequality, since <code>#</code> conflicts with the script |
| comment character. |
| |
| <br><dt><code>IN</code><dd>Set membership. Defined on set types and the types of their members. |
| Same precedence as <code><</code>. |
| |
| <br><dt><code>OR</code><dd>Boolean disjunction. Defined on boolean types. |
| |
| <br><dt><code>AND</code><span class="roman">, </span><code>&</code><dd>Boolean conjunction. Defined on boolean types. |
| |
| <br><dt><code>@</code><dd>The <span class="sc">gdb</span> “artificial array” operator (see <a href="Expressions.html#Expressions">Expressions</a>). |
| |
| <br><dt><code>+</code><span class="roman">, </span><code>-</code><dd>Addition and subtraction on integral and floating-point types, or union |
| and difference on set types. |
| |
| <br><dt><code>*</code><dd>Multiplication on integral and floating-point types, or set intersection |
| on set types. |
| |
| <br><dt><code>/</code><dd>Division on floating-point types, or symmetric set difference on set |
| types. Same precedence as <code>*</code>. |
| |
| <br><dt><code>DIV</code><span class="roman">, </span><code>MOD</code><dd>Integer division and remainder. Defined on integral types. Same |
| precedence as <code>*</code>. |
| |
| <br><dt><code>-</code><dd>Negative. Defined on <code>INTEGER</code> and <code>REAL</code> data. |
| |
| <br><dt><code>^</code><dd>Pointer dereferencing. Defined on pointer types. |
| |
| <br><dt><code>NOT</code><dd>Boolean negation. Defined on boolean types. Same precedence as |
| <code>^</code>. |
| |
| <br><dt><code>.</code><dd><code>RECORD</code> field selector. Defined on <code>RECORD</code> data. Same |
| precedence as <code>^</code>. |
| |
| <br><dt><code>[]</code><dd>Array indexing. Defined on <code>ARRAY</code> data. Same precedence as <code>^</code>. |
| |
| <br><dt><code>()</code><dd>Procedure argument list. Defined on <code>PROCEDURE</code> objects. Same precedence |
| as <code>^</code>. |
| |
| <br><dt><code>::</code><span class="roman">, </span><code>.</code><dd><span class="sc">gdb</span> and Modula-2 scope operators. |
| </dl> |
| |
| <blockquote> |
| <em>Warning:</em> Set expressions and their operations are not yet supported, so <span class="sc">gdb</span> |
| treats the use of the operator <code>IN</code>, or the use of operators |
| <code>+</code>, <code>-</code>, <code>*</code>, <code>/</code>, <code>=</code>, , <code><></code>, <code>#</code>, |
| <code><=</code>, and <code>>=</code> on sets as an error. |
| </blockquote> |
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