std::strings: minor improvements

std/strings/strings.jule

@@ -22,43 +22,14 @@ fn Repeat(s: str, mut n: int): str {
     ret ss.Str()
 }
 
-fn hasPrefix(&s: str, &sub: str, mut start: int): bool {
-    if len(sub) == 0 || len(s)-start < len(sub) {
-        ret false
-    }
-
-    mut i := 0
-    for i < len(sub); i, start = i + 1, start + 1 {
-        if s[start] != sub[i] {
-            ret false
-        }
-    }
-    ret true
-}
-
 // Reports string has prefix as specified substring or not.
 fn HasPrefix(s: str, sub: str): bool {
-    ret hasPrefix(s, sub, 0)
-}
-
-fn hasSuffix(&s: str, &sub: str, mut start: int): bool {
-    if len(sub) == 0 || len(s)-start < len(sub) {
-        ret false
-    }
-
-    start = len(s) - start
-    mut i := 0
-    for i < len(sub); i++ {
-        if s[start-i-1] != sub[len(sub)-i-1] {
-            ret false
-        }
-    }
-    ret true
+    ret len(s) >= len(sub) && s[:len(sub)] == sub
 }
 
 // Reports string has suffix as specified substring or not.
 fn HasSuffix(s: str, sub: str): bool {
-    ret hasSuffix(s, sub, 0)
+    ret len(s) >= len(sub) && s[len(s)-len(sub):] == sub
 }
 
 // Returns index of first matched item with specified substring,
@@ -70,7 +41,7 @@ fn FindAt(s: str, sub: str, mut i: int): int {
         ret -1
     }
     for i < len(s); i++ {
-        if hasPrefix(s, sub, i) {
+        if HasPrefix(s[i:], sub) {
             ret i
         }
     }