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D.4.2.5 alg_kernel
Procedure from library algebra.lib (see algebra_lib).
- Usage:
- alg_kernel(phi,pr[,s,c]); phi map to basering, pr preimage ring,
s string (name of kernel in pr), c integer.
- Return:
- a string, the kernel of phi as string.
If, moreover, a string s is given, the algorithm creates, in the
preimage ring pr the kernel of phi with name s.
Three different algorithms are used depending on c = 1,2,3.
If c is not given or c=0, a heuristically best method is chosen.
(algorithm 1 uses the preimage command)
- Note:
- Since the kernel of phi lives in pr, it cannot be returned to the
basering. If s is given, the user has access to it in pr via s.
The basering may be a quotient ring.
Example:
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