Dan Piponi wrote:
On 8/30/07, Andrew Coppin <[EMAIL PROTECTED]> wrote:
Obviously you might very well have *meant* to write x = f x. But would
it be possible to add some kind of optional compiler warning to find
such assignments?
The thing that convinced me to learn Haskell in the first place was
the fact that you could write x = f x. Equations where you refer to
the same variable on the left and right hand sides are the bread of
butter and mathematics, and I was really pleased to find a programming
language that let me do the same.
Yeah, but... programs aren't like mathematics. I know people claim that
they are, but they aren't.
In mathematics, if you write "x = f y" you mean that these two
expressions are equal. In Haskell, if you say "x = f y" you mean *make*
then equal!
(Let us not even go into the times when expressions like "z = f z"
actually means "z[n+1] = f [z]"...)
So to me the idea of having a
warning for this is a bit like putting a sign on bottled water saying
"Warning: Contents may be wet". But that's just me. :-)
Well, it's definitely a valid thing to want to do, which is why I asked
for a *warning* not an error. ;-) Still, this seems to be an extremely
common way for me to hurt myself, so...
Still, it might be useful to for the compiler to warn when a newly
introduced name shadows another one.
...or that...
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