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

Richard O'Keefe ok at cs.otago.ac.nz
Wed Dec 9 18:16:15 EST 2009

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.

> 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.

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.

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