At Sun, 18 Dec 2011 09:14:00 -0500, Harry Spier wrote: > I saw on another list (Stack Overflow) a comment that Racket letrec > was equivalent to R5RS and R6RS letrec*, but when I checked the Racket > reference manual section 2.9 I didn't see any mention of strict left > to right evaluation. > --------------------------------------------- > (letrec ([id val-expr] ...) body ...+) > > Similar to let, but the locations for all ids are created first and > filled with #<undefined>, and all ids are bound in all val-exprs as > well as the bodys. The ids must be distinct according to > bound-identifier=?. > ------------------------------------------- > > 1.) Can someone verify for me whether Racket letrec is equivalent to > RnRS letrec* or to RnRS letrec.
"Similar to let" is meant to imply left-to-right evaluation, but I'll adjust the docs to clarify. > 2) Also how in Racket do you set an id to #<undefined> . I was unable > to find an (undefined) function returning #<undefined> similar to > (void) returning #<void> . There isn't one, but you can write (define (undefined) (letrec ([x x]) x)) _________________________________________________ For list-related administrative tasks: http://lists.racket-lang.org/listinfo/users
