From d739b05adf4ab0b012db9334ad2e406e5979fdaa Mon Sep 17 00:00:00 2001
From: dos-reis <gdr@axiomatics.org>
Date: Sat, 11 May 2013 15:08:29 +0000
Subject: Fix location of opposite? implementation

---
 src/algebra/catdef.spad.pamphlet | 4 ++--
 src/algebra/sf.spad.pamphlet     | 2 ++
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/src/algebra/catdef.spad.pamphlet b/src/algebra/catdef.spad.pamphlet
index a864ed03..fa6edba6 100644
--- a/src/algebra/catdef.spad.pamphlet
+++ b/src/algebra/catdef.spad.pamphlet
@@ -203,7 +203,7 @@ LinearSet(S: SemiGroup): Category == Join(LeftLinearSet S, RightLinearSet S)
 -- following domain must be compiled with subsumption disabled
 AbelianGroup(): Category == Join(CancellationAbelianMonoid, LeftLinearSet Integer) with
       -: % -> %           ++ \spad{-x} is the additive inverse of \spad{x}    
-      "-": (%,%) -> %     ++ \spad{x-y} is the difference of \spad{x} 
+      -: (%,%) -> %       ++ \spad{x-y} is the difference of \spad{x} 
                           ++ and \spad{y} i.e. \spad{x + (-y)}.
     add
       (x:% - y:%):% == x+(-y)
@@ -215,6 +215,7 @@ AbelianGroup(): Category == Join(CancellationAbelianMonoid, LeftLinearSet Intege
           zero? n => 0
           positive? n => double(n pretend PositiveInteger,x)
           double((-n) pretend PositiveInteger,-x)
+      opposite?(x,y) == x = -y
 
 @
 
@@ -1438,7 +1439,6 @@ OrderedAbelianGroup(): Category ==
       positive? x => x
       negative? x => -x
       0
-    opposite?(x,y) == x = -y
 @
 
 \section{category OAMON OrderedAbelianMonoid}
diff --git a/src/algebra/sf.spad.pamphlet b/src/algebra/sf.spad.pamphlet
index fc01b769..c64c6cba 100644
--- a/src/algebra/sf.spad.pamphlet
+++ b/src/algebra/sf.spad.pamphlet
@@ -506,6 +506,8 @@ DoubleFloat(): Join(FloatingPointSystem, DifferentialRing,
       x ** (n::% / d::%)
 
    nan? x == %fNaN? x
+   opposite?(x,y) == x = -y
+   annihilate?(x,y) == zero? x or zero? y
 @
 
 \section{License}
-- 
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