2 files changed, 7 insertions(+), 10 deletions(-)

M fmt/print.ha
M strings/sub.ha

@@ 83,7 83,9 @@ case void =>
 case let r: rune =>
 	return io::write(out, utf8::encoderune(r));
 case let s: str =>
-	if (mod.prec != 0) s = strings::sub(s, 0, mod.prec);
+	if (mod.prec > 0 && mod.prec < len(s)) {
+		s = strings::sub(s, 0, mod.prec);
+	};
 	return io::write(out, strings::toutf8(s));
 case let b: bool =>
 	return io::write(out, strings::toutf8(if (b) "true" else "false"));

@@ 6,18 6,15 @@ use encoding::utf8;
 export type end = void;
 
 fn utf8_byte_len_bounded(iter: *iterator, end: size) size = {
-	let pos = 0z;
 	for (let i = 0z; i < end; i += 1) {
 		let r = match (next(iter)) {
 		case let r: rune =>
 			yield r;
 		case void =>
-			break;
+			abort("index exceeds string length");
 		};
-
-		pos += utf8::runesz(r);
 	};
-	return pos;
+	return iter.dec.offs;
 };
 
 // Returns a substring in the range [start, end - 1], where each argument is the


@@ 29,14 26,12 @@ fn utf8_byte_len_bounded(iter: *iterator, end: size) 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);
+		assert(start <= sz, "start is higher than end");
+		yield utf8_byte_len_bounded(&iter, sz - start);
 	case =>
 		yield len(s);
 	};