At Mon, 02 Aug 2010 20:42:34 +0900 (JST), Keiko Nakata wrote: > This code prints "hi" twice, > > (define d (box #f)) > > (+ (begin (let/cc k (begin (set-box! d k) 3))) (begin (print "hi") 9)) > > ((unbox d) 0) > > whereas this prints "hi" once > > (define d (box #f)) > > (begin (begin (let/cc k (begin (set-box! d k) 3))) (print "hi")) > > ((unbox d) 0) > > Why?
Each form at the top level is wrapped in a prompt, and the content of a top-level `begin' is spliced into the top level. The latter program is the same as (define d (box #f)) (let/cc k (begin (set-box! d k) 3)) (print "hi") ((unbox d) 0) where there's an implicit prompt around the `let/cc' form. _________________________________________________ For list-related administrative tasks: http://lists.racket-lang.org/listinfo/users
