[plt-scheme] Re: frtime qn - behaviour depending on evt & another behaviour

no, actually the function is deliberately ignoring the value of e and
using a.
 the intention was that the behaviour b, should update every time evt
fires but not actually use the value of evt directly.
 instead b uses a, another behaviour. a in turn depends on evt. so, i
was thinking that when evt fires, a's value will change, and b will
use the new value of a when updating itself.
this does happen, but the value changes in a strange way.