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I tried to run this on my computer now, but as a complete Prolog noob, I'm having errors running the script? How do you load the http_open module/library in the

I tried to run this on my computer now, but as a complete Prolog noob, I'm having errors running the script? How do you load the http_open module/library in the first place? I tried following some Prolog tutorials in the past but I always get stuck trying to run something in the REPL. I'm using scryer-prolog. Thanks in advance!

triska 5y ago
The libraries I mentioned can be loaded by invoking the use_module/1 predicate on the toplevel, here is the complete transcript that loads the SGML, HTTP and XPath libraries in Scryer Prolog: ?- use_module(library(sgml)). true. ?- use_module(library(http/http_open)). true. ?- use_module(library(xpath)). true. The second query also uses portray_clause/1 from library(format), which you can load with: ?- use_module(library(format)). true. After all these libraries are loaded, you can post the sample queries from above, and it should work. There are also other ways to load these libraries: A very common way to load a library is to use the use_module/1 directive in Prolog source files. In that case, you would put for example the following 4 directives in a Prolog source file, say sample.pl: :- use_module(library(sgml)). :- use_module(library(http/http_open)). :- use_module(library(xpath)). :- use_module(library(format)). And then run sample.pl with: $ scryer-prolog sample.pl You can then again post the goals from above on the toplevel, and it will work too. Another way is to put these directives in your ~/.scryerrc configuration file, which is automatically consulted when Scryer Prolog starts. I recommend to do this for libraries you frequently need. Common candidates for this are for example library(dcgs), library(lists) and library(reif). Personally, I start Scryer Prolog from within Emacs, and I have set up Emacs so that I can consult a buffer with Prolog code, and also post queries and interact with the Prolog toplevel from within Emacs.
- pandatigox 5y ago
  Wow that works fantastically! Thank you for that. It almost seems like magic.

triska 5y ago

The libraries I mentioned can be loaded by invoking the use_module/1 predicate on the toplevel, here is the complete transcript that loads the SGML, HTTP and XPath libraries in Scryer Prolog: ?- use_module(library(sgml)). true. ?- use_module(library(http/http_open)). true. ?- use_module(library(xpath)). true. The second query also uses portray_clause/1 from library(format), which you can load with: ?- use_module(library(format)). true. After all these libraries are loaded, you can post the sample queries from above, and it should work. There are also other ways to load these libraries: A very common way to load a library is to use the use_module/1 directive in Prolog source files. In that case, you would put for example the following 4 directives in a Prolog source file, say sample.pl: :- use_module(library(sgml)). :- use_module(library(http/http_open)). :- use_module(library(xpath)). :- use_module(library(format)). And then run sample.pl with: $ scryer-prolog sample.pl You can then again post the goals from above on the toplevel, and it will work too. Another way is to put these directives in your ~/.scryerrc configuration file, which is automatically consulted when Scryer Prolog starts. I recommend to do this for libraries you frequently need. Common candidates for this are for example library(dcgs), library(lists) and library(reif). Personally, I start Scryer Prolog from within Emacs, and I have set up Emacs so that I can consult a buffer with Prolog code, and also post queries and interact with the Prolog toplevel from within Emacs.

pandatigox 5y ago
Wow that works fantastically! Thank you for that. It almost seems like magic.