Add 'e' to Floating typeclass

[chessai .]

Yeah, I think it probably shouldn't be added to the typeclass then.

The asymmetry should probably be mentioned in the report though.


On Wed, Feb 20, 2019, 9:22 PM Carter Schonwald <carter.schonwald at gmail.com>
wrote:

> either way, we're not gonna add e :)
>
> On Wed, Feb 20, 2019 at 8:30 AM Yitzchak Gale <gale at sefer.org> wrote:
>
>> Lennart's question "Is it really worth it?" is the most important one.
>> And no, probably it isn't.
>>
>> But Chessai is correct that this is a weird asymmetry in the Floating
>> class. My own experience is that I user neither e nor pi very much,
>> but neither one more than the other.
>>
>> Branch cuts of inverse trig functions are not relevant. The report
>> doesn't explicitly state this, but it's clear that these functions are
>> expected to return the standard ranges of values as in other
>> programming languages. You can be quite certain that acos (-1) is pi
>> in Haskell. And in fact, we have (at least on my computer)
>>
>> Prelude> acos (-1) == pi
>> True
>>
>> So there isn't any more or less reason to have e than pi as a separate
>> class member.
>>
>> On Sun, Feb 17, 2019 at 10:15 PM Lennart Augustsson
>> <lennart at augustsson.net> wrote:
>> >
>> > Is it really worth it?  How frequent are uses of e, except used like
>> exp?  On the other hand, pi has more frequent standalone use cases.
>> > Also, e has a simple definition (exp 1), whereas pi is somewhat more
>> involved.
>> >
>> > The logp1 and expm1 functions where added for good numerical reasons.
>> The same would not be true for e.
>> >
>> > On Sat, Feb 16, 2019 at 21:14 chessai . <chessai1996 at gmail.com> wrote:
>> >>
>> >> We have the 'pi' constant in the floating typeclass and some
>> trigonometric functions, as well as things like exp/log/expm1/log1p.
>> >>
>> >> Why not provide an 'e' constant?
>> >>
>> >> A default implementation could just be 'exp 1'.
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