30.8 Mappings that Respect Multiplication

  • RespectsMultiplication( mapp ) P

    Let mapp be a general mapping with underlying relation F Í S ×R, where S and R are the source and the range of mapp, respectively. Then RespectsMultiplication returns true if S and R are magmas such that (s1,r1), (s2,r2) Î F implies (s1 \* s2,r1 \* r2) Î F, and false otherwise.

    If mapp is single-valued then RespectsMultiplication returns true if and only if the equation s1^mapp * s2^mapp = (s1*s2)^mapp holds for all s1, s2 in S.

  • RespectsOne( mapp ) P

    Let mapp be a general mapping with underlying relation F Í S ×R, where S and R are the source and the range of mapp, respectively. Then RespectsOne returns true if S and R are magmas-with-one such that ( One(¢S¢), One(¢R¢) ) Î F, and false otherwise.

    If mapp is single-valued then RespectsOne returns true if and only if the equation One( S )^mapp = One( R ) holds.

  • RespectsInverses( mapp ) P

    Let mapp be a general mapping with underlying relation F Í S ×R, where S and R are the source and the range of mapp, respectively. Then RespectsInverses returns true if S and R are magmas-with-inverses such that (s,r) Î F implies (s-1,r-1) Î F, and false otherwise.

    If mapp is single-valued then RespectsInverses returns true if and only if the equation Inverse( s )^mapp = Inverse( s^mapp ) holds for all s in S.

    Mappings that are defined on a group and respect multiplication and inverses are group homomorphisms. Chapter Group Homomorphisms explains them in more detail.

  • IsGroupGeneralMapping( mapp ) P
  • IsGroupHomomorphism( mapp ) P

    A GroupGeneralMapping is a mapping which respects multiplication and inverses. If it is total and single valued it is called a group homomorphism.

  • KernelOfMultiplicativeGeneralMapping( mapp ) A

    Let mapp be a general mapping. Then KernelOfMultiplicativeGeneralMapping returns the set of all elements in the source of mapp that have the identity of the range in their set of images.

    (This is a monoid if mapp respects multiplication and one, and if the source of mapp is associative.)

  • CoKernelOfMultiplicativeGeneralMapping( mapp ) A

    Let mapp be a general mapping. Then CoKernelOfMultiplicativeGeneralMapping returns the set of all elements in the range of mapp that have the identity of the source in their set of preimages.

    (This is a monoid if mapp respects multiplication and one, and if the range of mapp is associative.)

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    GAP 4 manual
    February 2000