I have some data in a file in the following format: A)B B)C It describes nodes in a graph. The above would look like this if it were drawn out: A -> B -> C I want to write a Prolog program that can tell me if A can get to C, but I can’t seem to figure out how to open files, nor parse them into …

SWI-Prolog has two sections in the documentation that cover reading of data. One is about using terms , which is not what you want and the other is about reading primitive data which is probably what you want and is closest to the Python example you understand. As Paulo notes, using DCGs is the best…

Dear cpdean, DCGs are definitely worth studying. There are a number of examples within the SWI sources. Such as in library(csv). For something fast and dirty that depends on external packs (lib, & stoics_lib) : file grapho.pl :- use_module(library(lib)). :- lib(stoics_lib). :- debug(grapho). …

How do I run a prolog file as a script that exits? swipl my_file.pl always leaves it open in a repl/interpreter.

[image] cpdean: How do I run a prolog file as a script that exits? Disclaimer: it is still more useful to learn how to do stuff from the toplevel, but it takes time to get used to it. TL;DR: Use swipl -g <something> -g halt my_file.pl. But this depends on your “script”. I will use your previ…

[image] Boris: Use swipl -g <something> -g halt my_file.pl Hmmm … I use swipl -g <something> -t halt my_file.pl. See SWI-Prolog -- Running goals from the command line and SWI-Prolog -- Initialisation files and goals An alternative is to use the initialization directive in your script (the g…

Hi, I also get my “wisdom” from https://www.swi-prolog.org/pldoc/man?section=runoptions , I admit that I don’t truly undestand the difference between -g halt and -t halt. For the use case “run a prolog program as if it is a command line program, from the shell” it seems that the two are equivalent? N…

[image] Boris: I don’t truly understand the difference between -g halt and -t halt -t halt replaces the top-level REPL (interactive top level). If the goal (specified by the first -g parameter) throws an exception, I suspect that there are some situations where the result could be different; …

How do I load data from an arbitrary file format into prolog?

Help!

pmoura December 6, 2019, 6:52pm 2

You can write a simple parser for your file format using DCGs. For a nice tutorial, see:

http://www.pathwayslms.com/swipltuts/dcg/

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How do I load data from an arbitrary file format into prolog?

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