From: Markus Triska <triska@metalevel.at>
Date: Sun, 27 Aug 2023 07:56:30 +0000 (+0200)
Subject: ENHANCED: rudimentary implementation of normalize_space
X-Git-Tag: v0.9.2~2^2~1
X-Git-Url: https://git.sagredo.dev/?a=commitdiff_plain;h=9b96735615fa4f698454fe9a85d1022209dc6c1a;p=scryer-prolog.git

ENHANCED: rudimentary implementation of normalize_space

This removes leading and trailing whitespace from the text. Whitespace
within the string is not yet considered.
---

diff --git a/src/lib/xpath.pl b/src/lib/xpath.pl
index a871f78d..4ec01203 100644
--- a/src/lib/xpath.pl
+++ b/src/lib/xpath.pl
@@ -95,7 +95,8 @@
             op(200, fy, @)
           ]).
 
-:- use_module(library(lists),[member/2,memberchk/2]).
+:- use_module(library(lists),[member/2,memberchk/2,reverse/2]).
+:- use_module(library(charsio)).
 :- use_module(library(error)).
 :- use_module(library(dcgs)).
 :- use_module(library(si)).
@@ -636,5 +637,16 @@ text_of_1([C|Cs]) --> seq([C|Cs]).
 xsd_number_chars(Number, Chars) :-
         number_chars(Number, Chars).
 
-normalize_space(Text0, Text) :-
-        Text0 = Text.           % no conversion for the moment.
+normalize_space(Cs0, Cs) :-
+        must_be(chars, Cs0),
+        no_leading_whitespace(Cs0, Cs1),
+        reverse(Cs1, Cs2),
+        no_leading_whitespace(Cs2, Cs3),
+        reverse(Cs3, Cs).
+
+no_leading_whitespace([], []).
+no_leading_whitespace([C0|Cs0], Cs) :-
+        (   char_type(C0, whitespace) ->
+            no_leading_whitespace(Cs0, Cs)
+        ;   Cs = [C0|Cs0]
+        ).