# For SWI-Prolog documentation pages, show source appears only on pages for predicate

**URL:** <https://swi-prolog.discourse.group/t/for-swi-prolog-documentation-pages-show-source-appears-only-on-pages-for-predicate/5635>\
**Category:** Nice to know\
**Created:** [July 29, 2022, 9:43am UTC](https://swi-prolog.discourse.group/t/for-swi-prolog-documentation-pages-show-source-appears-only-on-pages-for-predicate/5635 "2022-07-29T09:43:13Z")\
**Posts on this page:** 1\
**Page:** 1

<div class="post-metadata">

**Author:** ![EricGT](https://avatars.discourse-cdn.com/v4/letter/e/f1d935/32.png) [@EricGT](https://swi-prolog.discourse.group/u/EricGT)\
**Post date:** [July 29, 2022, 9:43am UTC](https://swi-prolog.discourse.group/t/for-swi-prolog-documentation-pages-show-source-appears-only-on-pages-for-predicate/5635/1 "2022-07-29T09:43:13Z")

</div>

The [SWI-Prolog documentation pages for built-in predicates](https://www.swi-prolog.org/pldoc/man?section=builtin) have a nice feature to show the Prolog source code for a predicate by clicking on ![image](https://global.discourse-cdn.com/free1/uploads/swiprolog/original/2X/c/cc300d202d21c927683b3fa8121f9dcc829b2a78.png).

The feature only appears on the predicate page, e.g.

[setup\_call\_cleanup/3](https://www.swi-prolog.org/pldoc/doc_for?object=setup_call_cleanup/3)  
 ![image](https://global.discourse-cdn.com/free1/uploads/swiprolog/original/2X/5/551fe66ac8d2f23a8a31fd178e565a79da732644.png)

it does not appear on section pages, e.g.

[4.8 Meta-Call Predicates](https://www.swi-prolog.org/pldoc/man?section=metacall)  
 ![image](https://global.discourse-cdn.com/free1/uploads/swiprolog/original/2X/0/022ae21a09a5b6289dc619ad5e144d57c7532834.png)

If you expect the feature for a predicate and don’t see the icon, in the left table of index click on the specific predicate and the icon may be there.

* * *

Note: Some predicates are implemented in C and will not have the show source feature.

[split\_string/4](https://www.swi-prolog.org/pldoc/doc_for?object=split_string/4)  
 ![image](https://global.discourse-cdn.com/free1/uploads/swiprolog/original/2X/4/43ee8e459ce4418121eaa4d2b48fa4ce601b3c88.png)

To identify predicates implemented in C search C files (`*.c`) for `PRED_IMPL`, e.g.

> <https://github.com/SWI-Prolog/swipl-devel/blob/396ea38c50b014f23ab66fddaac824f621cc4ec5/src/pl-string.c#L302>