comparision of rational numbers no longer works in parameter rings

[gorzel]

Suppose the basering contains a parameter c, and variable x, characteritic 0.

In Singular 3-1-1, comparision of numbers involving parameters

like c/3 <c/2 or c2/2 < c always evaluated to 1.

In late Singular 3-1-2 this has changed to be evaluated to 0, with the effect

that a comparsion 1/3 < 1/2 give 0, too.

These computations should work again.

Note that comparsion for variables still give the expected result.

[An imitation for the number expressions is still restricted

since pardeg only considers the numerator.]

> system ("--version");
Singular for ix86-Linux version 3-1-2 (3120- 14066 )  Mar 25 2011 04:05:02

and already in 
> system("--version");
Singular for ix86-Linux version 3-1-2 (3120- 13552 )  Oct 22 2010 04:04:05

> ring rc = (0,c),(x,y),ds;

> 1/2>0;    // OK
1
> 1/2<0;    // OK
0
> 1/3<1/2;  // wrong
0
> 1/3-1/2<0;  // wrong
0
> 1/3-1/2;  
-1/6
> -1/2<0;     // wrong
0


> 1/3 < 1/2;   // wrong
0
> 1/3 > 1/2;
0
> 1/3 == 1/2;
0
> 1/3 != 1/2;
1

> c/3 < c/2;
0
> c/3 > c/2;
0
> c/3 == c/2;
0
> c/3 != c/2;
1

> x2/3 < x2/2;
1
> x2/3 > x2/2;
0
> x2/3 == x2/2;
0
> x2/3 != x2/2;
1

In 3-1-1 it did work as follows:

>  system("--version");
Singular for ix86-Linux version 3-1-1 (3110-2010030911)  Mar  9 2010 11:22:36
with

>  ring rc = (0,c),(x,y),dp;
> 1/3<1/2;   // OK
1
> 1/3>1/2;   // OK
0
> 1/3==1/2;
0
> 1/3!=1/2;
1
> c/2 > c/3;  // OK
1
> c/2 < c/3;  // wrong
1
> c/2 == c/3;
0
> c/2 != c/3;
1
> x2/3 < x2/2;  // OK
1
> x2/3 > x2/2;  // OK
0
> x2/3 == x2/2;
0
> x2/3 != x2/2;
1

> c2/3 <c;   // Wrong
1
> x2/3 <x;  // OK
0

[seelisch]

fixed by git commit 5b80583e0b5f470170ff83463359d005cd23ee23 (The behaviour need not be 100% as in 3-1-1 but re-establishes the simple cases like 1/3 < 1/2 and 1/3 * c < 1/ 2 * c...)

[gorzel]

Since, again, basic comparison of rational numbers no longer work in rings with parameters, I've reopened this ticket.

gorzelc@RAEUBER40:/tmp/SING/Singular/3-1-4/x86_64-Linux$ ./Singular -v
Singular for x86_64-Linux version 3-1-4 (3144- exported )  Jun 20 2012 08:04:22
with
	factory(@(#) factoryVersion = 3.1.4),libfac(3.1.3,March 2011),
	GMP(5.0),NTL(5.5.2),64bit,static readline,Plural,fan/cone,DBM,
	dynamic modules,OM_CHECK=0,OM_TRACK=0,random=1340208250

> ring rt =(0,t),x,dp;
> 1/2>1/3;  // wrong
0
> 1/3<1/2;  // wrong
0

[hannes]

fixed