Irr( G )
returns the list of irreducible characters of the group G.
If necessary the character table of G is computed.
The succession of characters is the same as in CharTable( G ).
    gap> Irr( SolvableGroup( "S4" ) );
    [ Character( S4, [ 1, 1, 1, 1, 1 ] ), 
      Character( S4, [ 1, 1, 1, -1, -1 ] ), 
      Character( S4, [ 2, 2, -1, 0, 0 ] ), 
      Character( S4, [ 3, -1, 0, 1, -1 ] ), 
      Character( S4, [ 3, -1, 0, -1, 1 ] ) ] 
GAP 3.4.4