forth: IF/ELSE/THEN + PC-driven body runner (+18)

2026-04-24 17:03:41 +00:00
parent 30d76537d1
commit b2939c1922
4 changed files with 238 additions and 3 deletions
--- a/lib/forth/tests/test-phase3.sx
+++ b/lib/forth/tests/test-phase3.sx
@@ -0,0 +1,123 @@
+;; Phase 3 — control flow (IF/ELSE/THEN, BEGIN/UNTIL/WHILE/REPEAT/AGAIN,
+;; DO/LOOP, return stack). Grows as each control construct lands.
+
+(define forth-p3-passed 0)
+(define forth-p3-failed 0)
+(define forth-p3-failures (list))
+
+(define
+  forth-p3-assert
+  (fn
+    (label expected actual)
+    (if
+      (= expected actual)
+      (set! forth-p3-passed (+ forth-p3-passed 1))
+      (begin
+        (set! forth-p3-failed (+ forth-p3-failed 1))
+        (set!
+          forth-p3-failures
+          (concat
+            forth-p3-failures
+            (list
+              (str label ": expected " (str expected) " got " (str actual)))))))))
+
+(define
+  forth-p3-check-stack
+  (fn
+    (label src expected)
+    (let ((r (forth-run src))) (forth-p3-assert label expected (nth r 2)))))
+
+(define
+  forth-p3-if-tests
+  (fn
+    ()
+    (forth-p3-check-stack
+      "IF taken (-1)"
+      ": Q -1 IF 10 THEN ; Q"
+      (list 10))
+    (forth-p3-check-stack
+      "IF not taken (0)"
+      ": Q 0 IF 10 THEN ; Q"
+      (list))
+    (forth-p3-check-stack
+      "IF with non-zero truthy"
+      ": Q 42 IF 10 THEN ; Q"
+      (list 10))
+    (forth-p3-check-stack
+      "IF ELSE — true branch"
+      ": Q -1 IF 10 ELSE 20 THEN ; Q"
+      (list 10))
+    (forth-p3-check-stack
+      "IF ELSE — false branch"
+      ": Q 0 IF 10 ELSE 20 THEN ; Q"
+      (list 20))
+    (forth-p3-check-stack
+      "IF consumes flag"
+      ": Q IF 1 ELSE 2 THEN ; 0 Q"
+      (list 2))
+    (forth-p3-check-stack
+      "absolute value via IF"
+      ": ABS2 DUP 0 < IF NEGATE THEN ; -7 ABS2"
+      (list 7))
+    (forth-p3-check-stack
+      "abs leaves positive alone"
+      ": ABS2 DUP 0 < IF NEGATE THEN ; 7 ABS2"
+      (list 7))
+    (forth-p3-check-stack
+      "sign: negative"
+      ": SIGN DUP 0 < IF DROP -1 ELSE DROP 1 THEN ; -3 SIGN"
+      (list -1))
+    (forth-p3-check-stack
+      "sign: positive"
+      ": SIGN DUP 0 < IF DROP -1 ELSE DROP 1 THEN ; 3 SIGN"
+      (list 1))
+    (forth-p3-check-stack
+      "nested IF (both true)"
+      ": Q 1 IF 1 IF 10 ELSE 20 THEN ELSE 30 THEN ; Q"
+      (list 10))
+    (forth-p3-check-stack
+      "nested IF (inner false)"
+      ": Q 1 IF 0 IF 10 ELSE 20 THEN ELSE 30 THEN ; Q"
+      (list 20))
+    (forth-p3-check-stack
+      "nested IF (outer false)"
+      ": Q 0 IF 0 IF 10 ELSE 20 THEN ELSE 30 THEN ; Q"
+      (list 30))
+    (forth-p3-check-stack
+      "IF before other ops"
+      ": Q 1 IF 5 ELSE 6 THEN 2 * ; Q"
+      (list 10))
+    (forth-p3-check-stack
+      "IF in chained def"
+      ": POS? 0 > ;
+       : DOUBLE-IF-POS DUP POS? IF 2 * THEN ;
+       3 DOUBLE-IF-POS"
+      (list 6))
+    (forth-p3-check-stack
+      "empty then branch"
+      ": Q 1 IF THEN 99 ; Q"
+      (list 99))
+    (forth-p3-check-stack
+      "empty else branch"
+      ": Q 0 IF 99 ELSE THEN ; Q"
+      (list))
+    (forth-p3-check-stack
+      "sequential IF blocks"
+      ": Q -1 IF 1 THEN -1 IF 2 THEN ; Q"
+      (list 1 2))))
+
+(define
+  forth-p3-run-all
+  (fn
+    ()
+    (set! forth-p3-passed 0)
+    (set! forth-p3-failed 0)
+    (set! forth-p3-failures (list))
+    (forth-p3-if-tests)
+    (dict
+      "passed"
+      forth-p3-passed
+      "failed"
+      forth-p3-failed
+      "failures"
+      forth-p3-failures)))