On Jan 18, 2007, at 17:00 , Philippe de Rochambeau wrote:

concat1 :: [[a]] -> [a] concat1 xss = [ x | xs <- xss, x <- xs ]

I would like to see what gets stored in xs.

Offhand:

import Debug.Trace

concat1 :: Show a => [[a]] -> [a] concat1 xss = [ x | xs <- xss, x <- trace (show xs) xs ]

(The Show qualification is kinda unfortunate.) -- brandon s. allbery [linux,solaris,freebsd,perl] allbery@kf8nh.com system administrator [openafs,heimdal,too many hats] allbery@ece.cmu.edu electrical and computer engineering, carnegie mellon university KF8NH