- re_foldl(:Goal, +Regex, +String, ?V0, ?V, +Options) is semidet
- Fold all matches of Regex on String. Each match is represented by a
dict as specified for re_matchsub/4. V0 and V are related using a
sequence of invocations of Goal as illustrated below.
call(Goal, Dict1, V0, V1), call(Goal, Dict2, V1, V2), ... call(Goal, Dictn, Vn, V).
This predicate is used to implement re_split/4 and re_replace/4. For example, we can count all matches of a Regex on String using this code:
re_match_count(Regex, String, Count) :- re_foldl(increment, Regex, String, 0, Count, []). increment(_Match, V0, V1) :- V1 is V0+1.After which we can query
?- re_match_count("a", "aap", X). X = 2.Here is an example Goal for extracting all the matches with their offsets within the string:
range_match(Dict, StringIndex-[MatchStart-Substring|List], StringIndex-List) :- Dict.(StringIndex.index) = MatchStart-MatchLen, sub_string(StringIndex.string, MatchStart, MatchLen, _, Substring).And can be used with this query (note the
capture_type(range)option, which is needed by range_match/3, andgreedy(false)to invert the meaning of*?):?- String = "{START} Mary {END} had a {START} little lamb {END}", re_foldl(range_match, "{START} *?(?<piece>.*) *?{END}", String, _{string:String,index:piece}-Matches, _-[], [capture_type(range),greedy(false)]). Matches = [8-"Mary", 33-"little lamb"].