@Override void apply(Env global, Env local) {
// Expect we can broadcast across all functions as needed.
Env env = local == null ? global : local;
Frame fr0 = null, fr1 = null;
double d0=0, d1=0;
if( env.isAry() ) fr1 = (Frame) env.pop(); else d1 = (double)env.pop(); //String k0 = env.key();
if( env.isAry() ) fr0 = (Frame) env.pop(); else d0 = (double)env.pop(); //String k1 = env.key();
if( fr0==null && fr1==null ) {
env.push(op(d0, d1));
return;
}