This library provides pure list-based I/O processing for Prolog, where the communication to the actual I/O device is performed transparently through coroutining. This module itself is just an interface to the actual implementation modules.
The following predicates are re-exported from other modules
- phrase_from_file(:Grammar, +File) is nondet
- Process the content of File using the DCG rule Grammar. The
space usage of this mechanism depends on the length of the not
committed part of Grammar. Committed parts of the temporary list
are reclaimed by the garbage collector, while the list is
extended on demand due to unification of the attributed tail
variable. Below is an example that counts the number of times a
string appears in a file. The library dcg/basics provides
string//1 matching an arbitrary string and remainder//1 which
matches the remainder of the input without parsing.
:- use_module(library(dcg/basics)). file_contains(File, Pattern) :- phrase_from_file(match(Pattern), File). match(Pattern) --> string(_), string(Pattern), remainder(_). match_count(File, Pattern, Count) :- aggregate_all(count, file_contains(File, Pattern), Count).
This can be called as (note that the pattern must be a string (code list)):
?- match_count('pure_input.pl', `file`, Count).
The following predicates are exported, but not or incorrectly documented.