Re: [Haskell-beginners] Structural restrictions in type constructor

Maybe not exactly what you need but this was for me a kind of eye-opener with regard to type system: https://github.com/leonidas/codeblog/blob/master/2013/2013-02-19-typesafe-ti... On Mon, Jun 22, 2015 at 9:09 PM, Rein Henrichs wrote:

You can't do this at the type level in Haskell.

On Mon, Jun 22, 2015 at 7:00 AM Matt Williams < matt.williams45.mw@gmail.com> wrote:

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OK, I think this is clearly well beyond my level!

Will insert some manual checking.

Thanks, Matt

On 22 June 2015 at 14:51, emacstheviking wrote:

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It *could* be done and might already have been done... I seem to recall a few months back somebody asked for a similar feature using one of the vector libraries, to limit one of the input vectors to a fixed length?

You'd have to dig through the list archives though...

On 22 June 2015 at 12:36, Imants Cekusins wrote:

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But this is checking the values in the implementation, not a type level build time guarantee, isn't it?

yep, correct. Could be caught by unit tests though :-P _______________________________________________ Beginners mailing list Beginners@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/beginners

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