From 1116287328fbcf21b78ffcfc80627213bc68184b Mon Sep 17 00:00:00 2001
From: Matthew Flatt <mflatt@racket-lang.org>
Date: Fri, 21 Jun 2019 12:33:20 -0600
Subject: [PATCH] adjust sqrt and log on -0.0

original commit: 098fdb7d197bda4cd1ecc9b68407ee72fcce9311
---
 mats/5_3.ms  | 4 ++++
 mats/ieee.ms | 6 +++---
 s/5_3.ss     | 4 ++--
 3 files changed, 9 insertions(+), 5 deletions(-)

diff --git a/mats/5_3.ms b/mats/5_3.ms
index ca8d4b7a37..09325a2963 100644
--- a/mats/5_3.ms
+++ b/mats/5_3.ms
@@ -2690,6 +2690,8 @@
     (error? (sqrt 3 4)) 
     (error? (sqrt 'a))
     (= (sqrt -1.0) 0.0+1.0i)
+    (eqv? (sqrt -0.0) -0.0)
+    (== (sqrt +nan.0) +nan.0)
     (eqv? (sqrt -1) +1i)
     (= (sqrt 9) 3)
     (= (sqrt 1/4) 1/2)
@@ -2741,6 +2743,8 @@
     (error? (log 0))
     (= (log 1) 0)
     (fl= (log 1.0) 0.0)
+    (eqv? (log 0.0) -inf.0)
+    (eqv? (log -0.0) -inf.0)
     (~= (log (exp 7)) 7) 
     (fl~= (log (exp 10.2)) 10.2)
     (cfl~= (log -1) (* pi +1.0i))
diff --git a/mats/ieee.ms b/mats/ieee.ms
index f623fdd5e0..b85a6f4ec7 100644
--- a/mats/ieee.ms
+++ b/mats/ieee.ms
@@ -413,7 +413,7 @@
 
 (mat sqrt
    ; from Kahan
-   (== (sqrt -0.0) +0.0+0.0i)
+   (== (sqrt -0.0) -0.0) ; the grounds that (negative? -0.0) => #f
    (== (sqrt -4.0) +0.0+2.0i)
    (== (sqrt -inf.0) +0.0+inf.0i)
    (== (sqrt 0.0+inf.0i) +inf.0+inf.0i)
@@ -505,7 +505,7 @@
    (== (log 1.0) 0.0)
    (== (log +inf.0) +inf.0)
 
-   (== (log -0.0) (make-rectangular -inf.0 +pi))
+   (== (log -0.0) -inf.0) ; on the grounds that (negative? -0.0) => #f
    (== (log -1.0) (make-rectangular 0.0 +pi))
    (== (log -inf.0) (make-rectangular +inf.0 +pi))
 
@@ -528,7 +528,7 @@
    (== (log 1.0) 0.0)
    (== (log +inf.0) +inf.0)
 
-   (== (log -0.0) (make-rectangular -inf.0 +pi))
+   (== (log -0.0) -inf.0)  ; on the grounds that (negative? -0.0) => #f
    (== (log -1.0) (make-rectangular 0.0 +pi))
    (== (log -inf.0) (make-rectangular +inf.0 +pi))
 
diff --git a/s/5_3.ss b/s/5_3.ss
index a57b3f06f8..10a19b0ee5 100644
--- a/s/5_3.ss
+++ b/s/5_3.ss
@@ -1324,7 +1324,7 @@
       [(x)
        (type-case x
          [(flonum?)
-          (if (negated-flonum? x)
+          (if (fl< x 0.0)
               (fl-make-rectangular ($fllog (fl- x)) pi)
               ($fllog x))]
          [($inexactnum?) (cfllog x)]
@@ -1527,7 +1527,7 @@
    (lambda (x)
       (type-case x
          [(flonum?)
-          (if (and (negated-flonum? x) (not ($nan? x)))
+          (if (fl< x 0.0)
               (fl-make-rectangular 0.0 ($flsqrt (flabs x)))
               ($flsqrt x))]
          [($inexactnum?) (cflsqrt x)]