Re: [Haskell-cafe] Numerics and Warnings

* Aleksey Khudyakov [2013-04-10 23:20:15+0400]

On 10 April 2013 22:25, Roman Cheplyaka wrote:

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* Barak A. Pearlmutter [2013-04-10 15:38:35+0100]

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In fiddling around with some numeric code in Haskell, I noticed some issues. Basically, you get warnings if you write

energy mass = mass * c^2

but not if you write

energy mass = mass * c * c

which seems a bit perverse. Some more examples are below.

I understand the inference issues that cause this, but common innocuous cases could---and I would argue, should---be addressed in ad-hoc ways.

Hi Barak,

In a sense, defaulting in Haskell *is* a mechanism to address common innocuous cases in an ad-hoc way (although it still has a relatively simple and easy to understand semantics).

This IS rather annoying problem for numeric code. Raising value to positive power is quite common operation yet ^ operator generally couldn't be used because it leads to warning about type defaulting (rightfully) and one wants to keep code warning free. Actually it's problem with warnings and I don't think adding some ad-hoc rules for generating warning is necessarily bad idea

You can disable the warning with -fno-warn-type-defaults. Roman