strings: add split_capital (#14716)

vlib/strings/strings.v

@@ -126,3 +126,24 @@ pub fn find_between_pair_string(input string, start string, end string) string {
 	}
 	return ''
 }
+
+// split_capital returns an array containing the contents of `s` split by capital letters.
+// Example: assert strings.split_capital('XYZ') == ['X', 'Y', 'Z']
+// Example: assert strings.split_capital('XYStar') == ['X', 'Y', 'Star']
+pub fn split_capital(s string) []string {
+	mut res := []string{}
+	mut word_start := 0
+	for idx, c in s {
+		if c >= `A` && c <= `Z` {
+			if word_start != idx {
+				res << s#[word_start..idx]
+			}
+			word_start = idx
+			continue
+		}
+	}
+	if word_start != s.len {
+		res << s#[word_start..]
+	}
+	return res
+}

vlib/strings/strings_test.v

@@ -94,3 +94,14 @@ fn test_find_between_pair_family() {
 		assert '$e1' == '$e2'
 	}
 }
+
+fn test_split_capital() {
+	assert strings.split_capital('') == []
+	assert strings.split_capital('abc') == ['abc']
+	assert strings.split_capital('X') == ['X']
+	assert strings.split_capital('XX') == ['X', 'X']
+	assert strings.split_capital('XYZ') == ['X', 'Y', 'Z']
+	assert strings.split_capital('JohnWilliams') == ['John', 'Williams']
+	assert strings.split_capital('JDStar') == ['J', 'D', 'Star']
+	assert strings.split_capital('cpDumpRotarySpring') == ['cp', 'Dump', 'Rotary', 'Spring']
+}