"interact" behaves oddly if used interactively

[Dean Herington]

On Wed, 1 Oct 2003, Keith Wansbrough wrote:

> > Can actually someone supply an implementation of something like interact 
> > that does no pipelining for the argument "id"? Simply doing "putStr !$ f 
> > !$ s" was not enough!
> 
> Yes, of course.
> 
> Your code above only forces the evaluation of the first cons-cell of
> the list, which is not enough.  You want to force the entire list.
> Try
> 
> deepSeq :: [a] -> b -> b
> deepSeq (x:xs) y = deepSeq xs y
> deepSeq [] y = y
> 
> noninteract f = do
>   s <- getContents
>   putStr (f (deepSeq s s))


Here's another way to write the above:

import DeepSeq
noninteract f = getContents >>= (putStr . f $!!)

-- Dean