Add String.trim_left() / right() (#1773)

* Add String.trim_left() / right()

* Fix formatting

lib/std/core/string.c3

@@ -145,14 +145,40 @@ fn String join_new(String[] s, String joiner, Allocator allocator = allocator::h
  @return `a substring of the string passed in`
 *>
 fn String String.trim(string, String to_trim = "\t\n\r ")
+{
+    return string.trim_left(to_trim).trim_right(to_trim);
+}
+
+<*
+ Remove characters from the front of a string.
+
+ @param [in] string `The string to trim`
+ @param [in] to_trim `The set of characters to trim, defaults to whitespace`
+ @pure
+ @return `a substring of the string passed in`
+*>
+fn String String.trim_left(string, String to_trim = "\t\n\r ")
 {
 	usz start = 0;
 	usz len = string.len;
 	while (start < len && char_in_set(string[start], to_trim)) start++;
 	if (start == len) return string[:0];
-	usz end = len - 1;
-	while (end > start && char_in_set(string[end], to_trim)) end--;
-	return string[start..end];
+	return string[start..];
+}
+
+<*
+ Remove characters from the end of a string.
+
+ @param [in] string `The string to trim`
+ @param [in] to_trim `The set of characters to trim, defaults to whitespace`
+ @pure
+ @return `a substring of the string passed in`
+*>
+fn String String.trim_right(string, String to_trim = "\t\n\r ")
+{
+	usz len = string.len;
+	while (len > 0 && char_in_set(string[len - 1], to_trim)) len--;
+	return string[:len];
 }
 
 <*

releasenotes.md

@@ -70,6 +70,7 @@
 - Updated hash function.
 - Added URL parser.
 - Added convenience functions to `Maybe`.
+- Added `String.trim_left()` and `.trim_right()`.
 
 ## 0.6.5 Change list
 

test/unit/stdlib/core/string.c3

@@ -59,6 +59,7 @@ fn void test_ends_with()
 	assert(s.ends_with(""));
 	assert(!s.ends_with("e"));
 }
+
 fn void test_trim()
 {
 	String s = " \t\nabc ";
@@ -67,6 +68,29 @@ fn void test_trim()
 	assert("  \n\tok".trim() == "ok");
 	assert("!! \n\t ".trim() == "!!");
 	assert(s.trim("c \t") == "\nab");
+	assert("".trim() == "");
+
+
+}
+
+fn void test_trim_left()
+{
+	String s = " \t\nabc ";
+	assert(s.trim_left() == "abc ");
+	assert("\n\t".trim_left() == "");
+	assert("  \n\tok".trim_left() == "ok");
+	assert("!! \n\t ".trim_left() == "!! \n\t ");
+	assert("".trim_left() == "");
+}
+
+fn void test_trim_right()
+{
+	String s = " \t\nabc ";
+	assert(s.trim_right() == " \t\nabc");
+	assert("\n\t".trim_right() == "");
+	assert("  \n\tok".trim_right() == "  \n\tok");
+	assert("!! \n\t ".trim_right() == "!!");
+	assert("".trim_right() == "");
 }
 
 fn void test_split()
@@ -175,4 +199,4 @@ fn void! test_hex_conversion()
 {
 	assert("0x123aCd".to_long()! == 0x123acd);
 	assert("123acD".to_long(16)! == 0x123acd);
-}
+}