string: add trim_prefix and trim_suffix

.gitignore

@@ -15,6 +15,7 @@
 *.lib
 *.bak
 a.out
+.noprefix.vrepl_temp
 
 # ignore v build files
 /v.c
@@ -22,6 +23,7 @@ a.out
 /v.c.out
 .vrepl_temp.v
 fns.txt
+.noprefix.vrepl_temp.v
 
 # ignore temp directories
 /temp

vlib/builtin/string.v

@@ -926,6 +926,20 @@ pub fn (s string) trim_right(cutset string) string {
 	return if pos < 0 { '' } else { s.left(pos + 1) }
 }
 
+pub fn (s string) trim_prefix(str string) string {
+	if s.starts_with(str) {
+		return s.replace(str, "")
+	}
+	return s
+}
+
+pub fn (s string) trim_suffix(str string) string {
+	if s.ends_with(str) {
+		return s.replace(str, "")
+	}
+	return s
+}
+
 // fn print_cur_thread() {
 // //C.printf("tid = %08x \n", pthread_self());
 // }

vlib/builtin/string_test.v

@@ -25,6 +25,12 @@ fn test_add() {
 fn test_ends_with() {
 	a := 'browser.v'
 	assert a.ends_with('.v')
+
+	s := 'V Programming Language'
+	assert s.ends_with('guage') == true
+	assert s.ends_with('Language') == true
+	assert s.ends_with('Programming Language') == true
+	assert s.ends_with('V') == false
 }
 
 fn test_between() {
@@ -646,6 +652,27 @@ fn test_repeat() {
 	// TODO Add test for negative values
 }
 
+fn test_starts_with() {
+	s := 'V Programming Language'
+	assert s.starts_with('V') == true
+	assert s.starts_with('V Programming') == true
+	assert s.starts_with('Language') == false
+}
+
+fn test_trim_prefix() {
+	s := 'V Programming Language'
+	assert s.trim_prefix('V ') == 'Programming Language'
+	assert s.trim_prefix('V Programming ') == 'Language'
+	assert s.trim_prefix('Language') == s
+}
+
+fn test_trim_suffix() {
+	s := 'V Programming Language'
+	assert s.trim_suffix(' Language') == 'V Programming'
+	assert s.trim_suffix(' Programming Language') == 'V'
+	assert s.trim_suffix('V') == s
+}
+
 fn test_raw() {
 	raw := r'raw\nstring'
 	lines := raw.split('\n')