kill(all);

defs : [l=a-h, h=a-l];

implicit evaluation alone

l;

single explicit evaluation

ev(l,defs);

twice nested evaluation (or twice repeated)

ev( ev(l,defs) , defs );

ev(l,defs,eval);

three times repeated evaluation

ev( ev( ev(l,defs) , defs ), defs);

ev(l,defs,eval,eval);

not completely equal..

infinite evaluation is recursive

ev(l,defs);
ev(l,defs,eval);
ev(l,defs,eval,eval);
ev(l,defs,eval,eval,eval);
ev(l,defs,eval,eval,eval,eval);

ev(l,defs,infeval);