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Added function to string.m to split strings up into lists of `words'.

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Added function to string.m to split strings up into lists of `words'.

library/string.m
	Added string__length/1 function.

library/string.m
	Added function string__words/2.
This commit is contained in:
Ralph Becket
2000-04-27 09:31:46 +00:00
parent eb135d2e23
commit 687e33f261
1 changed files with 57 additions and 0 deletions
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57
library/string.m
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@@ -214,6 +214,16 @@
% list__foldl(Closure, Chars, Acc0, Acc)
% but is implemented more efficiently.)
:- func string__words(pred(char), string) = list(string).
:- mode string__words(pred(in) is semidet, in) = out is det.
% string__words(SepP, String) returns the list of
% non-empty substrings of String (in first to last
% order) that are delimited by non-empty sequences
% of chars matched by SepP. For example,
%
% string__words(char__is_whitespace, " the cat sat on the mat") =
% ["the", "cat", "sat", "on", "the", "mat"]
:- pred string__split(string, int, string, string).
:- mode string__split(in, in, out, out) is det.
% string__split(String, Count, LeftSubstring, RightSubstring):
@@ -1988,6 +1998,8 @@ string__special_precision_and_width(-1).
:- interface.
:- func string__length(string) = int.
:- func string__append(string, string) = string.
:- func string__char_to_string(char) = string.
@@ -2045,6 +2057,9 @@ string__special_precision_and_width(-1).
:- implementation.
string__length(S) = L :-
string__length(S, L).
string__append(S1, S2) = S3 :-
string__append(S1, S2, S3).
@@ -2124,6 +2139,48 @@ string__hash(S) = N :-
string__format(S1, PT) = S2 :-
string__format(S1, PT, S2).
% ---------------------------------------------------------------------------- %
string__words(SepP, String) = Words :-
I = preceding_boundary(isnt(SepP), String, string__length(String) - 1).
Words = words_2(SepP, String, I, []).
% ---------------------------------------------------------------------------- %
:- func words_2(pred(char), string, int, list(string)) = list(string).
:- mode words_2(pred(in) is semidet, in, in, in) = out is det.
words_2(SepP, String, WordEnd, Words0) = Words :-
( if WordEnd < 0 then
Words = Words0
else
WordPre = preceding_boundary(SepP, String, WordEnd),
Word = string__unsafe_substring(String, WordPre + 1,
WordEnd - WordPre),
PrevWordEnd = preceding_boundary(isnt(SepP), String, WordPre),
Words = words_2(SepP, String, PrevWordEnd, [Word | Words0])
).
% ---------------------------------------------------------------------------- %
% preceding_boundary(SepP, String, I) returns the largest index J =< I
% in String of the char that is SepP and min(-1, I) if there is no
% such J. preceding_boundary/3 is intended for finding (in reverse)
% consecutive maximal sequences of chars satisfying some property.
% Note that I *must not* exceed the largest valid index for String.
:- func preceding_boundary(pred(char), string, int) = int.
:- mode preceding_boundary(pred(in) is semidet, in, in) = out is det.
preceding_boundary(SepP, String, I) =
( if I < 0 then
I
else if SepP(string__unsafe_index(String, I)) then
I
else
preceding_boundary(SepP, String, I - 1)
).
% ---------------------------------------------------------------------------- %
% ---------------------------------------------------------------------------- %