53.10 IsCharacter

IsCharacter( obj )

returns true if obj is a character, and false otherwise. For a class function obj that does not know whether it is a character, the scalar products with all irreducible characters of the source of obj are computed. If they are all integral and nonegative then obj is turned into a character record.

    gap> psi:= ClassFunction( S4, S4.charTable.centralizers );
    ClassFunction( S4, [ 24, 8, 3, 4, 4 ] )
    gap> IsCharacter( psi ); psi;
    true
    Character( S4, [ 24, 8, 3, 4, 4 ] )
    gap> cf:= ClassFunction( S4, irr[3] - irr[1] );
    ClassFunction( S4, [ 1, 1, -2, -1, -1 ] )
    gap> IsCharacter( cf ); cf;
    false
    VirtualCharacter( S4, [ 1, 1, -2, -1, -1 ] ) 

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