[GAP Forum] how to get variables in symbolic expression

[Lee Martin CCNP]

Hi 
maple can use op(1, poly)
how to do similar things in gap?
[ [ y, z, x+z ] ]
poly1 := 0;for j in Length(prepoly1[1]) do  poly1 := poly1 + prepoly1[1][3]
become y + z + x*z
Regards,
Martin