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| <title>The GNU Fortran Compiler: PRESENT</title> |
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| <a name="PRESENT-_002d_002d_002d-Determine-whether-an-optional-dummy-argument-is-specified"></a> |
| <h3 class="section">9.209 <code>PRESENT</code> — Determine whether an optional dummy argument is specified</h3> |
| <a name="index-PRESENT"></a> |
| |
| <dl compact="compact"> |
| <dt><em>Description</em>:</dt> |
| <dd><p>Determines whether an optional dummy argument is present. |
| </p> |
| </dd> |
| <dt><em>Standard</em>:</dt> |
| <dd><p>Fortran 95 and later |
| </p> |
| </dd> |
| <dt><em>Class</em>:</dt> |
| <dd><p>Inquiry function |
| </p> |
| </dd> |
| <dt><em>Syntax</em>:</dt> |
| <dd><p><code>RESULT = PRESENT(A)</code> |
| </p> |
| </dd> |
| <dt><em>Arguments</em>:</dt> |
| <dd><table> |
| <tr><td width="15%"><var>A</var></td><td width="70%">May be of any type and may be a pointer, scalar or array |
| value, or a dummy procedure. It shall be the name of an optional dummy argument |
| accessible within the current subroutine or function.</td></tr> |
| </table> |
| |
| </dd> |
| <dt><em>Return value</em>:</dt> |
| <dd><p>Returns either <code>TRUE</code> if the optional argument <var>A</var> is present, or |
| <code>FALSE</code> otherwise. |
| </p> |
| </dd> |
| <dt><em>Example</em>:</dt> |
| <dd><div class="smallexample"> |
| <pre class="smallexample">PROGRAM test_present |
| WRITE(*,*) f(), f(42) ! "F T" |
| CONTAINS |
| LOGICAL FUNCTION f(x) |
| INTEGER, INTENT(IN), OPTIONAL :: x |
| f = PRESENT(x) |
| END FUNCTION |
| END PROGRAM |
| </pre></div> |
| </dd> |
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