[Haskell-cafe] Re: Suggestions for improvement

[N. Raghavendra]

At 2010-10-05T09:21:51+13:00, Richard O'Keefe wrote:

> answer s = concat $ zipWith replicate [1..] s
>
> I looked at the examples and said, "hmm, elements are being repeated
> varying numbers of times".  Looked up "repeat", found that that was
> the wrong function, and saw "replicate", which is the right one:
> 	replicate n x = [x ..... x] with n copies of x
> So zipWith [1..] "abcd" is ["a", "bb", "ccc", "dddd"]
> and pasting those together is just what concat does.
>
> Had replicate, zipWith, concat not already been provided, I might
> have done one of two things.

Many thanks for the detailed explanation.  It is instructive because I
thought of a solution in a different way.  Another lesson is that I must
know the Prelude well.  I've also installed `pointfree'.  Together with
Hlint, it seems a useful tool for learning; for one thing, both of them
tell me about functions I didn't know earlier.

Regards,
Raghavendra.

-- 
N. Raghavendra <raghu at mri.ernet.in> | http://www.retrotexts.net/
Harish-Chandra Research Institute   | http://www.mri.ernet.in/
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