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#342 axiom from CVS not building on Fedora core 6 ←	↑	→ #344 Tube Plots

#343 Bug in FreeAbelianGroup

Edit detail for #343 Bug in FreeAbelianGroup revision 5 of 5

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Editor: japp Time: 2008/10/16 11:21:36 GMT-7
Note:

changed:
-
-From japp Thu Oct 16 11:09:05 -0700 2008
-From: japp
-Date: Thu, 16 Oct 2008 11:09:05 -0700
-Subject: 
-Message-ID: <20081016110905-0700@axiom-wiki.newsynthesis.org>
-
-Status: fix proposed => fixed somewhere 
-
-
-From japp Thu Oct 16 11:21:13 -0700 2008
-From: japp
-Date: Thu, 16 Oct 2008 11:21:13 -0700
-Subject: 
-Message-ID: <20081016112113-0700@axiom-wiki.newsynthesis.org>
-
-Status: fixed somewhere => fix proposed 
-

The order in FreeAbelianGroup is broken and makes the domain unusable (e.g., comparison of Set FreeAbelianGroup S does not work properly) For example here is a cycle:

  ----------------------------------------
  Z2:=FreeAbelianGroup Symbol         

  a:= a::FreeAbelianGroup Symbol         
  b:= b::FreeAbelianGroup Symbol
  z:= 0::FreeAbelianGroup Symbol

  a < -b 
  -b < z
  z < a
  ----------------------------------------

thus

axiom

a:= a::FreeAbelianGroup Symbol

$\label{eq1}a$

(1)

Type: FreeAbelianGroup(Symbol)

axiom

b:= b::FreeAbelianGroup Symbol

$\label{eq2}b$

(2)

Type: FreeAbelianGroup(Symbol)

axiom

z:= 0::FreeAbelianGroup Symbol

$\label{eq3}0$

(3)

Type: FreeAbelianGroup(Symbol)

axiom

(a < -b)::Boolean

$\label{eq4} \mbox{\rm false}$

(4)

Type: Boolean

axiom

(-b < z)::Boolean

$\label{eq5} \mbox{\rm true}$

(5)

Type: Boolean

axiom

(z < a)::Boolean

$\label{eq6} \mbox{\rm true}$

(6)

Type: Boolean

proposed patch in the last few lines of free.spad:

  545,546c545,546
  <         ta.gen < tb.gen => true
  <         ta.gen > tb.gen => false
  ---
  >         ta.gen < tb.gen => tb.exp > 0
  >         ta.gen > tb.gen => ta.exp < 0

apparently revlex order is intended but is not achieved in the current implementation, as the sign of the trailing exponent is not taken into account.

Fixed in wh-sandbox Revision: 496 --kratt6, Mon, 09 Apr 2007 13:50:56 -0500 reply

Status: open => fix proposed

... --gdr, Wed, 21 May 2008 02:20:15 -0700 reply

Fixed in OpenAxiom