Feat: prelude and new words

tests/forth/generator.rs

@@ -102,3 +102,43 @@ fn geom_zero_count() {
 fn geom_underflow() {
     expect_error("1 2 geom..", "stack underflow");
 }
+
+#[test]
+fn step_range_ascending() {
+    expect_stack("0 1 0.25 .,", &[
+        int(0),
+        Value::Float(0.25, None),
+        Value::Float(0.5, None),
+        Value::Float(0.75, None),
+        int(1),
+    ]);
+}
+
+#[test]
+fn step_range_descending() {
+    expect_stack("1 0 -0.5 .,", &[
+        int(1),
+        Value::Float(0.5, None),
+        int(0),
+    ]);
+}
+
+#[test]
+fn step_range_integer_step() {
+    expect_stack("0 6 2 .,", &[int(0), int(2), int(4), int(6)]);
+}
+
+#[test]
+fn step_range_single() {
+    expect_stack("5 5 1 .,", &[int(5)]);
+}
+
+#[test]
+fn step_range_zero_step_error() {
+    expect_error("0 10 0 .,", "step cannot be zero");
+}
+
+#[test]
+fn step_range_underflow() {
+    expect_error("0 1 .,", "stack underflow");
+}