[Haskell-cafe] Numerics and Warnings

[Roman Cheplyaka]

* Aleksey Khudyakov <alexey.skladnoy at gmail.com> [2013-04-10 23:20:15+0400]
> On 10 April 2013 22:25, Roman Cheplyaka <roma at ro-che.info> wrote:
> > * Barak A. Pearlmutter <barak at cs.nuim.ie> [2013-04-10 15:38:35+0100]
> >> 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