sub_string/5

Availability:built-in

sub_string(+String, ?Before, ?Length, ?After, ?SubString)

SubString is a substring of String. There are Before characters in String before SubString, SubString contains Length character and is followed by After characters in String. If not enough information is provided to compute the start of the match, String is scanned left-to-right. This predicate is functionally equivalent to sub_atom/5, but operates on strings. The following example splits a string of the form <name>=<value> into the name part (an atom) and the value (a string).

name_value(String, Name, Value) :-
        sub_string(String, Before, _, After, "="), !,
        sub_string(String, 0, Before, _, NameString),
        atom_string(Name, NameString),
        sub_string(String, _, After, 0, Value).