Lazy in racket

How2lazy in DrRacket?

There's the lazy library, but it's not functional, i.e. I define a to be 1, define b as a + a, force b, it gives 2, but then I force set a to be 5, and it gives b as 2 again.

Any way around this?

>>6
Heh, I was thinking "Scheme" as in "the way the interpreter (and theory) worked in the SICP videos"

So then what's the solution, if neither of these are functional?

Is there a way to turn off caching in Racket/Scheme?