Add sf:enable-true-unspecific

diff --git a/src/sf/object.scm b/src/sf/object.scm
index 818fffff7c528fa78431bf56b6244ecc5376f7ad..c796cf3915f8b0d9a1bcb6bb4365f45315e391c6 100644 (file)
--- a/src/sf/object.scm
+++ b/src/sf/object.scm
@@ -448,6 +448,18 @@ USA.
   (and (constant? expression)
        (eq? (constant/value expression) value)))
 
+;; If true, then expression/unspecific? will return #t on
+;; unspecific which will enable certain operations to treat
+;; the value as something more convenient.  For example, a
+;; conditional might just treat an unspecific as #F to enable
+;; folding.
+(define sf:enable-true-unspecific? #t)
+
+(define (expression/unspecific? expression)
+  (and (constant? expression)
+       (eq? (constant/value expression) unspecific)
+       (noisy-test sf:enable-true-unspecific? "Enable true unspecific")))
+
 (define-integrable (global-ref/make name)
   (access/make #f
               (constant/make #f system-global-environment)
@@ -647,6 +659,12 @@ USA.
             alternative
             (sequence/make scode (list predicate alternative))))
 
+       ((and (expression/unspecific? predicate)
+             (noisy-test sf:enable-conditional-folding? "Fold constant unspecific conditional"))
+        (if (expression/effect-free? predicate)
+            alternative
+            (sequence/make scode (list predicate alternative))))
+
        ;; (if (not e) c a) => (if e a c)
        ((and (expression/call-to-not? predicate)
              (noisy-test sf:enable-conditional-inversion? "Conditional inversion"))
@@ -664,7 +682,8 @@ USA.
 
        ;; (if (if e1 e2 #f) <expr> K) => (if e1 (if e2 <expr> K) K)
        ((and (conditional? predicate)
-             (expression/constant-eq? (conditional/alternative predicate) #f)
+             (or (expression/constant-eq? (conditional/alternative predicate) #f)
+                 (expression/unspecific? (conditional/alternative predicate)))
              (constant? alternative)
              (noisy-test sf:enable-conjunction-linearization? "Conjunction linearization"))
         (conditional/make scode