Singular Manual: isInvolution

| ##### 7.5.8.0. isInvolution Procedure from library `involut.lib` (see involut_lib). Usage: isInvolution(F); F is a map from current ring to itself Return: integer, 1 if F determines an involution and 0 otherwise Theory: involution is an antiautomorphism of order 2 Assume: F is a map from current ring to itself Example:
    LIB "involut.lib";
    def A = makeUsl(2); setring A;
    map I = A,-e,-f,-h; //correct antiauto involution
    isInvolution(I);
    ==> 1
    map J = A,3*e,1/3*f,-h; // antiauto but not involution
    isInvolution(J);
    ==> 0
    map K = A,f,e,-h; // not antiauto
    isInvolution(K);
    ==> 0
See also: findInvo; involution; isAntiEndo.

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