[Haskell-cafe] ANNOUNCE: unicode-symbols-0.1.1

[Roel van Dijk]

2009/12/10 Richard O'Keefe <ok at cs.otago.ac.nz>:
> On Dec 10, 2009, at 2:58 AM, Roel van Dijk wrote:
>> I tried to be conservative with the choice of unicode symbols. I have
>> defined the division sign (÷) to be (/). But it could just as well be
>> defined as 'div'.
>
> No it couldn't.  One expects 3÷2 to be 1½, not 1.
> You will, for example, find this text on the web:
> "Mathematically, the division sign is equivalent to the forward slash.
> Thus, for example, 4 ÷ 5 = 4/5 = 0.8"
> This is actually historically backwards.  When I was a nipper,
> 1/6 meant "one and six" or "eighteen pence" or at least three
> loaves of good bread.  As far as I'm aware, the use of "/"
> instead of "÷" is a computerism introduced in the days of 6 bit
> character sets.

Ok, this makes me happy I choose (/) instead of 'div'.

>> Another choice that could lead to some discussion is the definition of
>> (⊂) to be 'Data.Set.isProperSubsetOf' and (⊆) to be
>> 'Data.Set.isSubsetOf'. An alternative choice would be to have (⊊) for
>> 'isProperSubsetOf' and (⊂) for 'isSubsetOf'.
>
> Mathematicians may use the plain horseshoe for either subset or
> proper subset, depending on the author.  But I've never ever seen
> anyone use the horseshoe with an equals bar for proper subset;
> that would really make no sense.

As James Hall pointed out there is actually a tiny slash trough the
equal bar underneath the horseshoe. The fact that this is hard to see
is another reason why I choose the first option.

> I suggest that you take the Z formal specification language as your
> guide (plain horseshoe is proper subset, horseshoe with equal bar is
> subset-or-equal).  If you don't like Z, try B:  same thing.

Yes, this is how I have defined things in the current version.

Thank you for your comments,
Roel