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| <title>The GNU Fortran Compiler: STRUCTURE and RECORD</title> |
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| <a name="STRUCTURE-and-RECORD-1"></a> |
| <h4 class="subsection">6.2.1 <code>STRUCTURE</code> and <code>RECORD</code></h4> |
| <a name="index-STRUCTURE"></a> |
| <a name="index-RECORD"></a> |
| |
| <p>Record structures are a pre-Fortran-90 vendor extension to create |
| user-defined aggregate data types. GNU Fortran does not support |
| record structures, only Fortran 90’s “derived types”, which have |
| a different syntax. |
| </p> |
| <p>In many cases, record structures can easily be converted to derived types. |
| To convert, replace <code>STRUCTURE /</code><var>structure-name</var><code>/</code> |
| by <code>TYPE</code> <var>type-name</var>. Additionally, replace |
| <code>RECORD /</code><var>structure-name</var><code>/</code> by |
| <code>TYPE(</code><var>type-name</var><code>)</code>. Finally, in the component access, |
| replace the period (<code>.</code>) by the percent sign (<code>%</code>). |
| </p> |
| <p>Here is an example of code using the non portable record structure syntax: |
| </p> |
| <div class="example"> |
| <pre class="example">! Declaring a structure named ``item'' and containing three fields: |
| ! an integer ID, an description string and a floating-point price. |
| STRUCTURE /item/ |
| INTEGER id |
| CHARACTER(LEN=200) description |
| REAL price |
| END STRUCTURE |
| |
| ! Define two variables, an single record of type ``item'' |
| ! named ``pear'', and an array of items named ``store_catalog'' |
| RECORD /item/ pear, store_catalog(100) |
| |
| ! We can directly access the fields of both variables |
| pear.id = 92316 |
| pear.description = "juicy D'Anjou pear" |
| pear.price = 0.15 |
| store_catalog(7).id = 7831 |
| store_catalog(7).description = "milk bottle" |
| store_catalog(7).price = 1.2 |
| |
| ! We can also manipulate the whole structure |
| store_catalog(12) = pear |
| print *, store_catalog(12) |
| </pre></div> |
| |
| <p>This code can easily be rewritten in the Fortran 90 syntax as following: |
| </p> |
| <div class="example"> |
| <pre class="example">! ``STRUCTURE /name/ ... END STRUCTURE'' becomes |
| ! ``TYPE name ... END TYPE'' |
| TYPE item |
| INTEGER id |
| CHARACTER(LEN=200) description |
| REAL price |
| END TYPE |
| |
| ! ``RECORD /name/ variable'' becomes ``TYPE(name) variable'' |
| TYPE(item) pear, store_catalog(100) |
| |
| ! Instead of using a dot (.) to access fields of a record, the |
| ! standard syntax uses a percent sign (%) |
| pear%id = 92316 |
| pear%description = "juicy D'Anjou pear" |
| pear%price = 0.15 |
| store_catalog(7)%id = 7831 |
| store_catalog(7)%description = "milk bottle" |
| store_catalog(7)%price = 1.2 |
| |
| ! Assignments of a whole variable do not change |
| store_catalog(12) = pear |
| print *, store_catalog(12) |
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