Feat: demo songs

tests/forth/arithmetic.rs

@@ -210,3 +210,47 @@ fn shorthand_float() {
 fn shorthand_float_negative() {
     expect_float("-.5 1 +", 0.5);
 }
+
+// linmap
+
+#[test]
+fn linmap_basic() {
+    expect_float("64 0 127 200 2000 linmap", 200.0 + (64.0 / 127.0) * 1800.0);
+}
+
+#[test]
+fn linmap_at_bounds() {
+    expect_float("0 0 127 200 2000 linmap", 200.0);
+}
+
+#[test]
+fn linmap_at_upper() {
+    expect_float("127 0 127 200 2000 linmap", 2000.0);
+}
+
+#[test]
+fn linmap_equal_input_range() {
+    expect_float("5 5 5 100 200 linmap", 100.0);
+}
+
+// expmap
+
+#[test]
+fn expmap_at_zero() {
+    expect_float("0 200 8000 expmap", 200.0);
+}
+
+#[test]
+fn expmap_at_one() {
+    expect_float("1 200 8000 expmap", 8000.0);
+}
+
+#[test]
+fn expmap_midpoint() {
+    expect_float("0.5 100 10000 expmap", 1000.0);
+}
+
+#[test]
+fn expmap_negative_bound() {
+    expect_error("0.5 -100 8000 expmap", "expmap requires positive bounds");
+}