Re: Mark partial functions as such

Yup! Just wanted to make sure it didn't end up being the latter. On Thu, Aug 30, 2018, 10:19 PM Eric Mertens wrote:

I think this comes down to just documenting things like how strict functions are and how they behave on various classes of inputs. These are good things to document. It doesn’t just have to be about a boolean flag “partial” paste on a bunch of definitions.

On Aug 30, 2018, at 7:16 PM, Daniel Díaz Casanueva wrote:

Why not? I don't think mentioning that length doesn't work with infinite lists will do any harm.

I think many people make a distinction between partiality due to endless evaluation and partiality due to a call to "error". But I still think documenting either of both things can be helpful.

Best, Daniel

Am Fr., 31. Aug. 2018 um 04:09 Uhr schrieb David Feuer < david.feuer@gmail.com>:

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Yes, I think so. What about functions like length? length (repeat ()) is bottom. repeat () is not bottom. Ergo, length is partial. But I don't think we want to say that!

On Thu, Aug 30, 2018, 10:05 PM Daniel Díaz Casanueva < dhelta.diaz@gmail.com> wrote:

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+1 from me too. The partiality of a function seems to me like something that should be documented.

Best, Daniel

Am Fr., 31. Aug. 2018 um 02:10 Uhr schrieb Richard Eisenberg < rae@cs.brynmawr.edu>:

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Proposal: Mark partial functions in `base` as partial

Motivation: I'm about to teach Haskell to a classful of beginners. In my experience, they will soon reach for functions like `head` and `tail`, because pattern-matching is foreign to them. I would love just to be able to say "Don't use partial functions", but many students will not easily be able to tell partial functions from total ones.

I do expect this problem to work itself out rather quickly, and then students will be able to identify partial functions, but loudly marking partial functions as partial seems like a small service to everyone and a bigger one to newbies. I don't see any downsides.

Thoughts?

Thanks, Richard _______________________________________________ Libraries mailing list Libraries@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/libraries

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