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Support #1368

Improve manual for mod

Added by John Abbott over 4 years ago. Updated about 4 years ago.

Status:
Closed
Priority:
Normal
Assignee:
John Abbott
Category:
Manual/documentation
Target version:
CoCoA-5.3.0
Start date:
24 Nov 2019
Due date:
% Done:

100%

Estimated time:
0.77 h
Spent time:
0.75 h

Description

The manual entry for mod needs to be improved.

Ange recently reported that mod(a,p) = mod(b,p) did not work as she expected; the main point being that a and b has opposite signs.

Make the manual clearer.

Related issues

Related to CoCoALib - Design #1182: "mod" for BigIntClosed2018-05-04

History

#1 Updated by John Abbott over 4 years ago

  • Status changed from New to In Progress
  • % Done changed from 0 to 10

Currently the manual and the implementation are incompatible. The manual says that the remainder is always non-negative, but this is not true:

/**/ mod(-1,7);
-1

A very similar issue arose about a year ago in CoCoALib; it seems the CoCoA-5 manual was not checked/updated.
We should do this.

#2 Updated by John Abbott over 4 years ago

#3 Updated by John Abbott over 4 years ago

  • Status changed from In Progress to Resolved
  • Assignee set to John Abbott
  • % Done changed from 10 to 50

The solution to Ange's problem is to compute mod(a-b,p); this will be zero iff a and b are congruent modulo p.
Perhaps I should add this to the manual...??

#4 Updated by John Abbott over 4 years ago

  • Status changed from Resolved to Feedback
  • % Done changed from 50 to 90
  • Estimated time set to 0.77 h

I have updated the manual entry; I think it is clear now.

#5 Updated by John Abbott about 4 years ago

  • Status changed from Feedback to Closed
  • % Done changed from 90 to 100

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