# SWI-Prolog lynx library - doc error, I guess **URL:** \ **Category:** SWI-Prolog web site and services\ **Created:** [March 7, 2020, 12:19pm UTC](https://swi-prolog.discourse.group/t/swi-prolog-lynx-library-doc-error-i-guess/1978 "2020-03-07T12:19:52Z")\ **Posts on this page:** 5\ **Page:** 1
**Author:** ![dtonhofer](https://yyz2.discourse-cdn.com/free1/user_avatar/swi-prolog.discourse.group/dtonhofer/32/902_2.png) [@dtonhofer](https://swi-prolog.discourse.group/u/dtonhofer)\ **Post date:** [March 7, 2020, 12:19pm UTC](https://swi-prolog.discourse.group/t/swi-prolog-lynx-library-doc-error-i-guess/1978/1 "2020-03-07T12:19:52Z")
At [The documentation for “lynx”, weirdly titled “Title for pldoc(dir\_index)”](https://www.swi-prolog.org/pldoc/doc/_SWI_/library/lynx/index.html) the predicate `trim_line/2` is mentioned. This predicate does not exist! The correct name is `trim_spaces/2`. Defined in file `library/lynx/format.pl`, module `text_format`. Additionally, would it be possible to move this predicate to an autoloaded library? It’s rather useful. [library(readutil)](https://eu.swi-prolog.org/pldoc/doc/_SWI_/library/readutil.pl) seems like the right place. Or maybe [library(dcg/basics)](https://eu.swi-prolog.org/pldoc/man?section=basics) ---
**Author:** ![EricGT](https://avatars.discourse-cdn.com/v4/letter/e/f1d935/32.png) [@EricGT](https://swi-prolog.discourse.group/u/EricGT)\ **Post date:** [March 7, 2020, 12:54pm UTC](https://swi-prolog.discourse.group/t/swi-prolog-lynx-library-doc-error-i-guess/1978/2 "2020-03-07T12:54:29Z")
> [@dtonhofer](#): > > the predicate `trim_line/2` is mentioned. > > This predicate does not exist! I am not finding that to be the case on my system. Using Windows 10. ```prolog Welcome to SWI-Prolog (threaded, 64 bits, version 8.1.24) SWI-Prolog comes with ABSOLUTELY NO WARRANTY. This is free software. Please run ?- license. for legal details. For online help and background, visit https://www.swi-prolog.org For built-in help, use ?- help(Topic). or ?- apropos(Word). ?- use_module(library(lynx/format)). true. ?- string_codes(" a b c ",Codes_in),trim_line(Codes_in,Codes_out),string_codes(Line,Codes_out). Codes_in = Codes_out, Codes_out = [32, 97, 32, 98, 32, 99, 32], Line = " a b c ". ``` In the [documentation](https://www.swi-prolog.org/pldoc/doc/_SWI_/library/lynx/index.html) if you click on ![image](https://global.discourse-cdn.com/free1/uploads/swiprolog/original/1X/0a1ac5568086658351ac3bbb5f1e9ae25846fdfc.png) at the end of the line it will take you to the source code. What I did not expect based on just the name (trim\_line) was that it does not remove space codes or characters, but space tokens, e.g. `Remove leading and trailing white space (b(_,_)) tokens from a line.` so moving trim\_line/2 is not something I would vote for. ---
**Author:** ![dtonhofer](https://yyz2.discourse-cdn.com/free1/user_avatar/swi-prolog.discourse.group/dtonhofer/32/902_2.png) [@dtonhofer](https://swi-prolog.discourse.group/u/dtonhofer)\ **Post date:** [March 7, 2020, 1:08pm UTC](https://swi-prolog.discourse.group/t/swi-prolog-lynx-library-doc-error-i-guess/1978/3 "2020-03-07T13:08:13Z")
Thanks Eric. I’m using `8.1.19-37-gc4fb81227` (Thus, [dev branch](https://www.swi-prolog.org/download/devel), the [stable branch](https://www.swi-prolog.org/download/stable) has 8.0.3 still) ```prolog ?- use_module(library(lynx/format)). true. ?- string_codes(" a b c ",Codes_in), trim_line(Codes_in,Codes_out), string_codes(Line,Codes_out). ERROR: Unknown procedure: trim_line/2 (DWIM could not correct goal) ``` Damn you DWIM! But: ```prolog ?- string_codes(" a b c ",Codes_in), | trim_spaces(Codes_in,Codes_out), | string_codes(Line,Codes_out). Correct to: "text_format:trim_spaces(Codes_in,Codes_out)"? yes Codes_in = Codes_out, Codes_out = [32, 97, 32, 98, 32, 99, 32], Line = " a b c ". ``` So I may be ahead of the documentation. ---
**Author:** ![EricGT](https://avatars.discourse-cdn.com/v4/letter/e/f1d935/32.png) [@EricGT](https://swi-prolog.discourse.group/u/EricGT)\ **Post date:** [March 7, 2020, 1:09pm UTC](https://swi-prolog.discourse.group/t/swi-prolog-lynx-library-doc-error-i-guess/1978/4 "2020-03-07T13:09:21Z")
> [@dtonhofer](#): > > The correct name is `trim_spaces/2` . Searching the documentation for `trim_spaces` does not show `trim_spaces`. ![image](https://global.discourse-cdn.com/free1/uploads/swiprolog/original/1X/85d54b9b862e4d4e88a8d23199de3431bf55ae75.png) ```prolog Search Documentation: trim trim trim_line/2 trim_stacks/0 trimcore/0 trimcore/0 ``` [Searching](https://github.com/SWI-Prolog/swipl-devel/search?q=trim_spaces&unscoped_q=trim_spaces) the SWI-Prolog [source](https://github.com/SWI-Prolog/swipl-devel) at GitHub I also do not find `trim_spaces`. I did find [normalize\_space/2](https://www.swi-prolog.org/pldoc/man?predicate=normalize_space/2) ([src](https://github.com/SWI-Prolog/swipl-devel/blob/c2b0232935f995aadff87e2cab76265dd1203818/src/os/pl-ctype.c#L684)) ```prolog Welcome to SWI-Prolog (threaded, 64 bits, version 8.1.24) SWI-Prolog comes with ABSOLUTELY NO WARRANTY. This is free software. Please run ?- license. for legal details. For online help and background, visit https://www.swi-prolog.org For built-in help, use ?- help(Topic). or ?- apropos(Word). ?- normalize_space(string(String)," a b c "). String = "a b c". ``` 🙂 ---
**Author:** ![EricGT](https://avatars.discourse-cdn.com/v4/letter/e/f1d935/32.png) [@EricGT](https://swi-prolog.discourse.group/u/EricGT)\ **Post date:** [March 7, 2020, 1:47pm UTC](https://swi-prolog.discourse.group/t/swi-prolog-lynx-library-doc-error-i-guess/1978/5 "2020-03-07T13:47:32Z")
> [@dtonhofer](#): > > So I may be ahead of the documentation. I would say that you are behind the documentation. * * * Your version 8.1.19-37 has a [release](https://github.com/SWI-Prolog/swipl-devel/releases) date of 12/15/2019 * * * AFAIK the online documentation is updated with the Git code and may be there before a release is done. * * * On Feb 13, 2020 (02/13/2020) [format.pl](https://github.com/SWI-Prolog/swipl-devel/blob/61a937543314cc59ab46b33dc9abaed8c39fe222/library/lynx/format.pl) was updated with `trim_line/2` which also removed `trim_spaces/2` ([history](https://github.com/SWI-Prolog/swipl-devel/commits/master/library/lynx/format.pl)) Commit [b392c20e58e77d729aa880c132d393ee7a58ec30](https://github.com/SWI-Prolog/swipl-devel/commit/b392c20e58e77d729aa880c132d393ee7a58ec30) * * * On Feb 15, 2020 (02/15/2020) Release [8.1.22](https://swi-prolog.discourse.group/t/ann-swi-prolog-8-1-22/1867) occurred with the changes to format.pl. In checking the notes the only related item I found is > AUTOLOAD: Support HTML to text conversion (lynx subdir of library). Since SWI-Prolog is open source it was possible to find and put the details in this post. * * * Since my system has version `8.1.24` (03/04/2020) the changes made to format.pl are on my system. 🙂