1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
|
%****************************************************************************%
% FILE : string_extra.ml %
% DESCRIPTION : Additional functions for ML strings. %
% %
% READS FILES : <none> %
% WRITES FILES : <none> %
% %
% AUTHOR : R.J.Boulton %
% DATE : 4th March 1991 %
% %
% LAST MODIFIED : R.J.Boulton %
% DATE : 13th January 1992 %
%****************************************************************************%
%----------------------------------------------------------------------------%
% string_less : string -> string -> bool %
% %
% Lexicographical less-than on strings. %
%----------------------------------------------------------------------------%
let string_less s1 s2 =
letrec string_less' l1 l2 =
if (null l2) then false
if (null l1) then true
else let a1 = ascii_code (hd l1)
and a2 = ascii_code (hd l2)
in if (a1 < a2) then true
if (a1 = a2) then string_less' (tl l1) (tl l2)
else false
in string_less' (explode s1) (explode s2);;
|
