From: Taylor R Campbell <campbell@mumble.net>
Date: Wed, 28 Nov 2018 03:48:20 +0000 (+0000)
Subject: Explain what commute-flonum-predicate is doing.
X-Git-Tag: mit-scheme-pucked-10.1.7~3^2~160
X-Git-Url: https://birchwood-abbey.net/git?a=commitdiff_plain;h=f6d21b2fa378830653b34d6ce73dd54759e4e309;p=mit-scheme.git

Explain what commute-flonum-predicate is doing.
---

diff --git a/src/compiler/machines/x86-64/rulflo.scm b/src/compiler/machines/x86-64/rulflo.scm
index 3cdebd196..c0ad9be80 100644
--- a/src/compiler/machines/x86-64/rulflo.scm
+++ b/src/compiler/machines/x86-64/rulflo.scm
@@ -318,6 +318,10 @@ USA.
                       (flonum-source-reference! source)
                       operand))))
 
+;;; For predicate giving (if (predicate x y) a b), return the
+;;; equivalent (if (predicate* y x) a b).  The unary predicates are
+;;; treated as if y = 0.  (XXX Separate this into another function.)
+
 (define (commute-flonum-predicate predicate)
   (case predicate
     ((FLONUM-EQUAL? FLONUM-ZERO?) 'FLONUM-EQUAL?)