[Maxima-bugs] [ maxima-Bugs-3354672 ] Maxima hangs when assigning modulus:-3

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Bugs item #3354672, was opened at 2011-07-05 22:26
Message generated for change (Tracker Item Submitted) made by crategus
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Category: Lisp Core - Polynomials
Group: None
Status: Open
Resolution: None
Priority: 5
Private: No
Submitted By: Dieter Kaiser (crategus)
Assigned to: Nobody/Anonymous (nobody)
Summary: Maxima hangs when assigning modulus:-3

Initial Comment:
It does not make sense to assign a negative value to the option variable modulus, but the documentation says:

"Maxima will allow zero or a negative integer to be assigned to modulus,
although it is not clear if that has any useful consequences."

In fact Maxima hangs, when trying to assign a negative value, whose absolute value is a prime number. When assigning a value to the option variable modulus the function msetchk calls the function primep.  This function hangs. The user function $primep works for negative numbers, because first it takes the absolute value.

I suggest  to disallow the assignment of negative numbers to the option variable modulus in msetchk. Another possibility is to take the absolute value of the argument of the function primep in msetchk. 

Dieter Kaiser

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