Made a neat macro that I think this channel would be interested in: (guarded-block (define x (random 10)) (guard (even? x) (define message-template "X was even, X = ~a, returning early") (format message-template x)) (define y (random 10)) (guard (odd? y) (define message-template "Y was odd, Y = ~a, returning early") (format message-template y)) (+ x y))

the above expands into this: (block (define x (random 10)) (cond [(even? x) (define message-template "X was even, X = ~a, returning early") (format message-template x)] [else (define y (random 10)) (cond [(odd? y) (define message-template "Y was odd, Y = ~a, returning early") (format message-template y)] [else (+ x y)])]))

I have been using a binding form defr (short for define-random). A short example with just one clause:

(defr [(x y) (random 1 10)] #:where (> (+ x y) 5)]) This computes two random numbers and binds them to x and y. Then checks if the predicate (> (+ x y) 5) . If true we carry on, if not, a new set of numbers are generated until we find a pair that fullfills the predicate.

The form is useful, when you need to generate a set of numbers that needs to be in some relation to each other.

I like that you guarded-block has an expansion without let/ec.

Yeah I really want to avoid paying the cost of continuations

I think this version is something we could add directly to racket and make define support automatically