From 3fc60627eba85729d61335f94d6008e83d0c7764 Mon Sep 17 00:00:00 2001
From: Justin Ethier <justin.ethier@gmail.com>
Date: Tue, 7 Apr 2015 22:55:14 -0400
Subject: [PATCH] Experimenting with literal evaluation at compile time

---
 trans.scm | 25 ++++++++++++++++++++++---
 1 file changed, 22 insertions(+), 3 deletions(-)

diff --git a/trans.scm b/trans.scm
index 1661835a..0ef4d963 100644
--- a/trans.scm
+++ b/trans.scm
@@ -1554,7 +1554,10 @@
 
           ((app? ast)
            (let ((fn (app->fun ast)))
-             (if (lambda? fn)
+             (cond
+              ;((literal-app? ast)
+              ; (cps (apply (car ast) (cdr ast)) cont-ast))
+              ((lambda? fn)
                  (cps-list (app->args ast)
                            (lambda (vals)
                              (cons (list
@@ -1562,12 +1565,13 @@
                                      (lambda->formals fn)
                                      (cps-seq (cddr fn) ;(ast-subx fn)
                                                     cont-ast))
-                                    vals)))
+                                    vals))))
+              (else
                  (cps-list ast ;(ast-subx ast)
                            (lambda (args)
                               (cons (car args)
                                     (cons cont-ast
-                                          (cdr args))))))))
+                                          (cdr args)))))))))
 
           (else
            (error "unknown ast" ast))))
@@ -1615,6 +1619,21 @@
             (cps ast '%halt))))
     ast-cps))
 
+(define (literal-app? ast)
+  (and 
+    (pair? ast)
+    (prim? (car ast))
+    (not (equal? 'apply (car ast))) ;; Cannot always exec at compile time
+    (call/cc
+      (lambda (return)
+        (for-each
+          (lambda (expr)
+            (if (not (const? expr))
+              (return #f)))
+          (cdr ast))
+        #t))))
+
+
 ;; Closure-conversion.
 ;;
 ;; Closure conversion eliminates all of the free variables from every