Else if chains

examples/match.vr

@@ -0,0 +1,81 @@
+// match.vr — else-if chains and match statements.
+//   vr run examples/match.vr
+
+// classify returns a label using an else-if chain.
+fn classify(n) {
+	if n < 0 {
+		return "negative"
+	} else if n == 0 {
+		return "zero"
+	} else if n < 10 {
+		return "small"
+	} else {
+		return "big"
+	}
+}
+
+// describe names a number with a match statement.
+fn describe(n) {
+	match n {
+		0 {
+			println("nothing")
+		}
+		1 {
+			println("lonely")
+		}
+		2 {
+			println("a pair")
+		}
+		7 {
+			println("lucky")
+		}
+		else {
+			println("just " + n)
+		}
+	}
+}
+
+fn main() {
+	// else-if chain
+	println(classify(-5))
+	println(classify(0))
+	println(classify(7))
+	println(classify(100))
+
+	// match with else
+	describe(0)
+	describe(1)
+	describe(2)
+	describe(7)
+	describe(42)
+
+	// match on strings
+	let day = "fri"
+	match day {
+		"sat" {
+			println("weekend!")
+		}
+		"sun" {
+			println("weekend!")
+		}
+		else {
+			println("workday")
+		}
+	}
+
+	// match inside a loop (break/continue still work)
+	let found = 0
+	for i in 0..10 {
+		match i {
+			4 {
+				found = i
+				break
+			}
+			else {
+				// keep looking
+			}
+		}
+	}
+	println("found " + found)
+	assert found == 4
+}

examples/tests.vr

@@ -125,6 +125,66 @@ fn test_break_continue() {
 	assert odds[2] == 5
 }
 
+fn test_else_if() {
+	let score = 85
+	let grade = ""
+	if score >= 90 {
+		grade = "A"
+	} else if score >= 80 {
+		grade = "B"
+	} else if score >= 70 {
+		grade = "C"
+	} else {
+		grade = "F"
+	}
+	assert grade == "B"
+	assert 10 > 5
+}
+
+fn test_match() {
+	let total = 0
+	match 2 {
+		1 {
+			total = total + 1
+		}
+		2 {
+			total = total + 10
+		}
+		else {
+			total = total + 100
+		}
+	}
+	assert total == 10 // matched the 2 arm
+
+	// match on strings
+	let word = "cat"
+	let sound = ""
+	match word {
+		"dog" {
+			sound = "woof"
+		}
+		"cat" {
+			sound = "meow"
+		}
+		else {
+			sound = "?"
+		}
+	}
+	assert sound == "meow"
+
+	// no else arm: nothing runs when nothing matches
+	let hit = 0
+	match 99 {
+		1 {
+			hit = 1
+		}
+		2 {
+			hit = 2
+		}
+	}
+	assert hit == 0
+}
+
 fn test_failing() {
 	// this one is meant to fail — shows up in `vr test` output
 	assert 1 == 2