hare

commit 5c2da3a96c4ebaf8d8e15213b8969ae07f653854
parent c6f71bf417f1ae0387178201c217cf3118585319
Author: Drew DeVault <sir@cmpwn.com>
Date:   Fri, 19 Feb 2021 14:12:16 -0500

ascii: add strcmp

Diffstat:
A
ascii/strcmp.ha
 | 
36
++++++++++++++++++++++++++++++++++++

1 file changed, 36 insertions(+), 0 deletions(-)
diff --git a/ascii/strcmp.ha b/ascii/strcmp.ha
@@ -0,0 +1,36 @@
+use strings;
+
+// Compares two strings by their ASCII sort order. If either string is not
+// entirely composed of ASCII characters, void is returned. Otherwise, zero is
+// returned if the strings are equal, a negative value if a is less than b, or a
+// positive value if a is greater than b.
+export fn strcmp(a: str, b: str) (int | void) = {
+	let a = strings::iter(a), b = strings::iter(b);
+	for (true) {
+		let ra = match (strings::next(&a)) {
+			void => return match (strings::next(&b)) {
+				void => 0,
+				rune => -1,
+			},
+			r: rune => r,
+		};
+		let rb = match (strings::next(&b)) {
+			void => return 1,
+			r: rune => r,
+		};
+		if (!isascii(ra) || !isascii(rb)) {
+			return;
+		};
+		if (ra != rb) {
+			return ra: u32: int - rb: u32: int;
+		};
+	};
+};
+
+@test fn strcmp() void = {
+	assert(strcmp("ABC", "ABC") as int == 0);
+	assert(strcmp("ABC", "AB") as int == 1);
+	assert(strcmp("AB", "ABC") as int == -1);
+	assert(strcmp("BCD", "ABC") as int == 1);
+	assert(strcmp("ABC", "こんにちは") is void);
+};