# Difference between revisions of "HowTo:Use Modular Numbers"

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== Question == | == Question == | ||

− | What's wrong in this? | + | How can one compute with modular numbers? What's wrong in this? |

Use R::=Z/(5)[x]; | Use R::=Z/(5)[x]; | ||

5x+2y; | 5x+2y; |

## Revision as of 16:54, 29 November 2005

## Question

How can one compute with modular numbers? What's wrong in this?

Use R::=Z/(5)[x]; 5x+2y; 2y ------------------------------- 5=0; FALSE -------------------------------

Moreover this command throws an error

Use R::=Z/(5);

## Answer

Type(5); INT -------------------------------

5 is an integer, and integers do not depend on the current ring: could you imagine what would happen to a For cycle over Z/(2)? ;-)

If you want to use 5 as a modular number you should either use this syntax (similar to C/C++)

5 % 5; 0 % 5 -------------------------------

or embed your integer into the polynomial ring

Use R::=Z/(5)[x]; Poly(5); 0 -------------------------------

The creation of a polynomial ring with no indeterminated has been disabled to highlight this (unexpected?) behaviour.