hare

commit 6cf28f9723ec32d5b4727499b6567704265ca5a6
parent e25547dd9ccda4ebda96d4d0370709580d1a1c35
Author: KAAtheWise <KAAtheWise@protonmail.com>
Date:   Wed, 19 Apr 2023 10:08:20 +0000

strings::sub: Remove unneeded iteration

If the end type is passed as the left bound, the length of the string in
chars can be determined using len instead of iterating over it.

Signed-off-by: KAA the Wise <KAAtheWise@protonmail.com>

Diffstat:
M
strings/sub.ha
 | 
21
+++++----------------

1 file changed, 5 insertions(+), 16 deletions(-)
diff --git a/strings/sub.ha b/strings/sub.ha
@@ -22,21 +22,6 @@ fn utf8_byte_len_bounded(iter: *iterator, end: size) size = {
 	return pos;
 };
 
-fn utf8_byte_len_unbounded(iter: *iterator) size = {
-	let pos = 0z;
-	for (true) {
-		let r = match (next(iter)) {
-		case let r: rune =>
-			yield r;
-		case void =>
-			break;
-		};
-
-		pos += utf8::runesz(r);
-	};
-	return pos;
-};
-
 // Returns a substring in the range [start, end - 1], where each argument is the
 // index of the Nth rune. If the end argument is given as [[strings::end]], the
 // end of the substring is the end of the original string. The lifetime of the
@@ -46,13 +31,16 @@ fn utf8_byte_len_unbounded(iter: *iterator) size = {
 // may cause unexpected linguistic errors to arise. You may want to use a
 // third-party Unicode module instead.
 export fn sub(s: str, start: size, end: (size | end)) str = {
+	if (end is size) {
+		assert(start <= end as size, "start is higher than end");
+	};
 	let iter = iter(s);
 	let starti = utf8_byte_len_bounded(&iter, start);
 	let endi = match (end) {
 	case let sz: size =>
 		yield starti + utf8_byte_len_bounded(&iter, sz - start);
 	case =>
-		yield starti + utf8_byte_len_unbounded(&iter);
+		yield len(s);
 	};
 	let bytes = toutf8(s);
 	return fromutf8_unsafe(bytes[starti..endi]);
@@ -63,4 +51,5 @@ export fn sub(s: str, start: size, end: (size | end)) str = {
 	assert(sub("a string", 0, 1) == "a");
 	assert(sub("a string", 0, 3) == "a s");
 	assert(sub("a string", 2, 8) == "string");
+	assert(sub("a string", 4, 4) == "");
 };