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PEP-308 a "simplicity-first" alternative

Erik Max Francis max at alcyone.com
Wed Feb 12 18:12:27 EST 2003 
Michael Hudson wrote:

> In which context?  In my world, => is implication.  It's even
> $\implies$ in LaTeX, I think. -> is often used to denote a map.

In a logical context.  _VNR_ for instance uses the single horizontal
line -> arrow for logical implication (section 15.1).

> > In mathematics when the double line version is used, it's often used
> > to mean something else, like "is equivalent to" or "evaluates to."
> 
> Equivalent to is often <=>.  Using => to mean equivalence would be
> daft notation, even by mathematical standards.

Or <-> (again, _VNR_ section 15.1).  Equvalence to as in equivalence
classes is usually written as three horizontal bars, as we all know.

> I have seen => used to mean "evaluates to", but generally in a
> computer context.

Yes, though I've sene it used in mathematics as well.  When I wrote "is
equivalent to," I really meant "evaluates to" or "could be replaced
with," rather than the logical meaning of equivalence (if and only if),
or the meaning with respect to equivalence classes.

-- 
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