GAP 4.8.9 installation with standard packages -- copy to your CoCalc project to get it
LoadPackage( "Modules" ); t := VariableForHilbertPolynomial( ); chi := 1/12*t^4+2/3*t^3-1/12*t^2-17/3*t-5; P := CreateElementOfGrothendieckGroupOfProjectiveSpace( chi, 4 ); # P!.DisplayTwistedCoefficients := true; Assert( 0, AmbientDimension( P ) = 4 ); Assert( 0, Dimension( P ) = 4 ); Assert( 0, Degree( P ) = 2 ); c := ChernPolynomial( P ); ch := ChernCharacter( c ); ## Hirzebruch-Riemann-Roch Assert( 0, HilbertPolynomial( ch ) = chi );