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| <h3 class="section">8.1 Introduction to intrinsic procedures</h3> |
| |
| <p>The intrinsic procedures provided by GNU Fortran include all of the |
| intrinsic procedures required by the Fortran 95 standard, a set of |
| intrinsic procedures for backwards compatibility with G77, and a |
| selection of intrinsic procedures from the Fortran 2003 and Fortran 2008 |
| standards. Any conflict between a description here and a description in |
| either the Fortran 95 standard, the Fortran 2003 standard or the Fortran |
| 2008 standard is unintentional, and the standard(s) should be considered |
| authoritative. |
| |
| <p>The enumeration of the <code>KIND</code> type parameter is processor defined in |
| the Fortran 95 standard. GNU Fortran defines the default integer type and |
| default real type by <code>INTEGER(KIND=4)</code> and <code>REAL(KIND=4)</code>, |
| respectively. The standard mandates that both data types shall have |
| another kind, which have more precision. On typical target architectures |
| supported by <samp><span class="command">gfortran</span></samp>, this kind type parameter is <code>KIND=8</code>. |
| Hence, <code>REAL(KIND=8)</code> and <code>DOUBLE PRECISION</code> are equivalent. |
| In the description of generic intrinsic procedures, the kind type parameter |
| will be specified by <code>KIND=*</code>, and in the description of specific |
| names for an intrinsic procedure the kind type parameter will be explicitly |
| given (e.g., <code>REAL(KIND=4)</code> or <code>REAL(KIND=8)</code>). Finally, for |
| brevity the optional <code>KIND=</code> syntax will be omitted. |
| |
| <p>Many of the intrinsic procedures take one or more optional arguments. |
| This document follows the convention used in the Fortran 95 standard, |
| and denotes such arguments by square brackets. |
| |
| <p>GNU Fortran offers the <samp><span class="option">-std=f95</span></samp> and <samp><span class="option">-std=gnu</span></samp> options, |
| which can be used to restrict the set of intrinsic procedures to a |
| given standard. By default, <samp><span class="command">gfortran</span></samp> sets the <samp><span class="option">-std=gnu</span></samp> |
| option, and so all intrinsic procedures described here are accepted. There |
| is one caveat. For a select group of intrinsic procedures, <samp><span class="command">g77</span></samp> |
| implemented both a function and a subroutine. Both classes |
| have been implemented in <samp><span class="command">gfortran</span></samp> for backwards compatibility |
| with <samp><span class="command">g77</span></samp>. It is noted here that these functions and subroutines |
| cannot be intermixed in a given subprogram. In the descriptions that follow, |
| the applicable standard for each intrinsic procedure is noted. |
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