From 8309025e187c3e0f0f8fda6933dfdd89dc17ae1d Mon Sep 17 00:00:00 2001
From: WillClinger <will@ccs.neu.edu>
Date: Mon, 3 Jul 2017 09:03:33 -0400
Subject: [PATCH] Libraries now invoked only once under all circumstances
 (ticket #655).

---
 lib/R6RS/r6rs-expander.sch | 30 +++++++++++++++++++++++-------
 lib/R6RS/r6rsmode.sch      | 17 +----------------
 2 files changed, 24 insertions(+), 23 deletions(-)

diff --git a/lib/R6RS/r6rs-expander.sch b/lib/R6RS/r6rs-expander.sch
index cac51757..12e01308 100644
--- a/lib/R6RS/r6rs-expander.sch
+++ b/lib/R6RS/r6rs-expander.sch
@@ -2876,16 +2876,32 @@
     ;; For importing and evaluating stuff in the persistent 
     ;; interactive environment, see REPL above.
 
-    ;; FIXME:  Since expand-toplevel-sequence calls eval on every
-    ;; library in the sequence, the following procedure calls eval
-    ;; on every library twice.  That can double the compile time.
-    
+    ;; NOTE: expand-toplevel-sequence calls eval on every library
+    ;; in the sequence.  (It calls scan-sequence, which calls
+    ;; expand-library, which calls expand-library-or-program,
+    ;; which calls eval on the expanded library.)  That's why
+    ;; run-r6rs-sequence calls eval only on the expressions
+    ;; obtained by expanding the program, if present.
+    ;; See ticket #655.
+
     (define (run-r6rs-sequence forms)
       (with-toplevel-parameters
        (lambda ()
-         (for-each (lambda (exp) (eval exp (interaction-environment)))
-                   (expand-toplevel-sequence (normalize forms))))))
-    
+         (let* ((forms (normalize forms)))
+           (call-with-values
+            (lambda ()
+              (partition (lambda (form)
+                           (and (pair? form)
+                                (eq? 'program (car form))))
+                         forms))
+            (lambda (pgms libs)
+              (expand-toplevel-sequence libs)
+              (if (not (null? pgms))
+                  (let* ((exps (expand-toplevel-sequence pgms)))
+                    (for-each (lambda (exp)
+                                (eval exp (interaction-environment)))
+                              exps)))))))))
+
     (define (run-r6rs-program filename)
       (run-r6rs-sequence (read-file filename)))
 
diff --git a/lib/R6RS/r6rsmode.sch b/lib/R6RS/r6rsmode.sch
index a7d694e4..05567684 100644
--- a/lib/R6RS/r6rsmode.sch
+++ b/lib/R6RS/r6rsmode.sch
@@ -441,26 +441,11 @@
 ; loaded by load-r6rs-program.  The target-filename can be
 ; compiled before it is loaded.
 ;
-; FIXME:  This uses a hack to avoid compiling a library twice
-; in systems that compile on eval.  If the file contains only
-; one library, and nothing else, then we can compile to a file
-; and then load the file instead of calling eval on the result
-; of expansion.  That doesn't work if the file contains two
-; libraries and the second one imports from the first.
-;
 ; FIXME:  The io here should be protected against errors.
 
 (define (expand-r6rs-program filename target-filename)
   (larceny:load-r6rs-package)
-  (let ((nlibs (call-with-input-file
-                filename
-                (lambda (in)
-                  (do ((x (read in) (read in))
-                       (n 0 (if (pair? x) (+ n 1) n)))
-                      ((or (eof-object? x) (> n 1))
-                       n))))))
-    (parameterize ((larceny:r6rs-expand-only (= nlibs 1)))
-      (ex:expand-file filename target-filename))))
+  (ex:expand-file filename target-filename))
 
 ; This parameter determines whether expanded libraries
 ; and programs are evaluated immediately, as in van Tonder's