73.103 InverseDerivations

InverseDerivations( X, i )

When T[i] is a regular derivation, this function returns the position j such that T[j] is the inverse of T[i] in the Whitehead group. When T[i] is not regular, a list of values j is returned such that the inverse semigroup condition xyx = x, ; yxy = y is satisfied, where x = T[i], y = T[j]. Notice that derivation 8 has order 3 and derivation 15 as inverse.

    gap> inv4 := InverseDerivations( chi4 );
    [ 4 ]
    gap> inv8 := InverseDerivations( chi8 );
    [ 7, 8, 9 ]   

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GAP 3.4.4
April 1997