simp_mode - toggle rational simplification
rational simplification is called after nearly each operations on rationals. It is possible to toggle simplification on or off using simp_mode function.
simp_mod(%t) set rational simplification mode on
simp_mod(%f) set rational simplification mode off
mod=simp_mod() returns in mod the current rational simplification mode
s=poly(0,'s'); mod=simp_mode() simp_mode(%f);hns=s/s simp_mode(%t);hns=s/s simp_mode(mod);