booleans, comparisons, and if/else

examples/programs/control_flow/main.bro

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+# Milestone 5 foundation: booleans, comparisons, logical ops, if/else if/else.
+
+printf :: c_func(format *c_char, ...) c_int
+
+# Returns a distinct code per range using if / else if / else and comparisons.
+classify :: func(n i32) i32 {
+	if n < 0 {
+		return 1
+	} else if n == 0 {
+		return 2
+	} else if n >= 100 {
+		return 3
+	} else {
+		return 4
+	}
+}
+
+# A bool-returning function with a visible side effect, used to prove
+# short-circuit evaluation: it must only print when actually evaluated.
+noisy :: func() bool {
+	_ = printf("rhs-evaluated\n")
+	return true
+}
+
+main :: func() i32 {
+	total i32 = 0
+
+	# comparisons drive if / else if / else
+	total = total + classify(-5)   # 1
+	total = total + classify(0)    # 2
+	total = total + classify(250)  # 3
+	total = total + classify(42)   # 4  -> 10
+
+	# bool variables and logical and / or / not
+	a :: true
+	b :: false
+	if a and !b {
+		total = total + 10         # 20
+	}
+	if b or a {
+		total = total + 10         # 30
+	}
+	if !(a and b) {
+		total = total + 5          # 35
+	}
+
+	# block scoping: inner x shadows outer x, outer is unchanged after the block
+	x i32 = 1
+	if x == 1 {
+		x i32 = 100
+		if x == 100 {
+			total = total + 5      # 40
+		}
+	}
+	if x == 1 {
+		total = total + 2          # 42
+	}
+
+	# short-circuit: `false and noisy()` must NOT call noisy()
+	if false and noisy() {
+		_ = printf("unreachable-and\n")
+	}
+	# short-circuit: `true or noisy()` must NOT call noisy()
+	if true or noisy() {
+		_ = printf("or-taken\n")
+	}
+
+	return total                   # expect exit code 42
+}