[Haskell-cafe] For class Monoid; better names than mempty & mappend might have been: mid (mident) & mbinop

[Maciej Marcin Piechotka]

On Sun, 2011-07-24 at 19:29 +0100, Julian Porter wrote:
> 
> 
> 
> On 24 Jul 2011, at 19:19, KC wrote:
> 
> > I like the following but again "+" denotes addition and not a
> > general
> > binary operation.
> > 
> > 
> > > I personally often define the alias:
> > > 
> > > (<+>) = mappend
> > 
> > A lot of math books use "+" or "x" enclosed in a circle to indicate
> > that the usual meaning of "+" nor "x" is intended for the meaning of
> > the binary operation.
> > 
> 
> 
> Er no.  Both symbols have extremely precise meanings.  $\oplus$ is the
> direct sum of two modules and $\otimes$ is their tensor product.
> 

Well. Notation depends on branch. I've seen routinely used + as addition
in Z_{2,3,...} - for example 2 + 2 = 0.

For example λ have different meaning when you would say about
exponential distribution/radioactive decay and different when you talk
about wavelength. If you are using lambda calculus it have yet another
meaning. And according to http://en.wikipedia.org/wiki/Lambda those are
just 3 of many meanings.

I've seen ⊕ used as binary operation when the other were already used
before I learned that it may denote the direct sum.

Regards
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