From: Mark Wooding <mdw@distorted.org.uk>
Date: Sat, 3 Aug 2019 23:21:33 +0000 (+0100)
Subject: src/utilities.lisp (dosequence): Capture SEQ as a variable explicitly.
X-Git-Url: https://git.distorted.org.uk/~mdw/sod/commitdiff_plain/bacaaec3a2ba7e5fdbc342045f74394bc5ffbbcf

src/utilities.lisp (dosequence): Capture SEQ as a variable explicitly.

Previously it used `once-only', but that doesn't actually produce a
binding for constant expressions.
---

diff --git a/src/utilities.lisp b/src/utilities.lisp
index cb6f0cc..6e7a592 100644
--- a/src/utilities.lisp
+++ b/src/utilities.lisp
@@ -936,8 +936,9 @@
    The loop is surrounded by an anonymous BLOCK and the loop body forms an
    implicit TAGBODY, as is usual.  There is no result-form, however."
 
-  (once-only (:environment env seq start end)
-    (with-gensyms ((ivar "INDEX-") (endvar "END-") (bodyfunc "BODY-"))
+  (once-only (:environment env start end)
+    (with-gensyms ((seqvar "SEQ-") (ivar "INDEX-")
+		   (endvar "END-") (bodyfunc "BODY-"))
       (multiple-value-bind (docs decls body) (parse-body body :docp nil)
 	(declare (ignore docs))
 
@@ -946,13 +947,13 @@
 		 (let* ((do-vars nil)
 			(end-condition (if endvar
 					   `(>= ,ivar ,endvar)
-					   `(endp ,seq)))
+					   `(endp ,seqvar)))
 			(item (if listp
-				  `(car ,seq)
-				  `(aref ,seq ,ivar)))
+				  `(car ,seqvar)
+				  `(aref ,seqvar ,ivar)))
 			(body-call `(,bodyfunc ,item)))
 		   (when listp
-		     (push `(,seq (nthcdr ,start ,seq) (cdr ,seq))
+		     (push `(,seqvar (nthcdr ,start ,seqvar) (cdr ,seqvar))
 			   do-vars))
 		   (when indexp
 		     (push `(,ivar ,start (1+ ,ivar)) do-vars))
@@ -961,17 +962,18 @@
 		   `(do ,do-vars (,end-condition) ,body-call))))
 
 	  `(block nil
-	     (flet ((,bodyfunc (,var ,@(and indexvar `(,indexvar)))
-		      ,@decls
-		      (tagbody ,@body)))
-	       (etypecase ,seq
-		 (vector
-		  (let ((,endvar (or ,end (length ,seq))))
-		    ,(loopguts t nil endvar)))
-		 (list
-		  (if ,end
-		      ,(loopguts t t end)
-		      ,(loopguts indexvar t nil)))))))))))
+	     (let ((,seqvar ,seq))
+	       (flet ((,bodyfunc (,var ,@(and indexvar `(,indexvar)))
+			,@decls
+			(tagbody ,@body)))
+		 (etypecase ,seqvar
+		   (vector
+		    (let ((,endvar (or ,end (length ,seqvar))))
+		      ,(loopguts t nil endvar)))
+		   (list
+		    (if ,end
+			,(loopguts t t end)
+			,(loopguts indexvar t nil))))))))))))
 
 ;;;--------------------------------------------------------------------------
 ;;; Structure accessor hacks.