GAP Manual: 13.4. RoundCyc

RoundCyc( z )

returns the cyclotomic integer (see Cyclotomic Integers) with Zumbroich base coefficients (see ZumbroichBase) List( zumb, x -> Int( x+1/2 ) ) where zumb is the vector of Zumbroich base coefficients of the cyclotomic z; see also IntCyc.

    gap> RoundCyc( E(5)+1/2*E(5)^2 ); RoundCyc( 2/3*E(7)+3/2*E(4) );
    E(5)+E(5)^2
    -2*E(28)^3+E(28)^4-2*E(28)^11-2*E(28)^15-2*E(28)^19-2*E(28)^23
     -2*E(28)^27