Re: PROPOSAL: Restrict the type of (^), (^^), and add genericPower, genericPower'

On Sat, 17 Nov 2007, David Benbennick wrote:

I vote against this proposal.

On 11/17/07, Ian Lynagh wrote:

...

In my experience this would remove 99.9% of all defaulting (mostly where you write things like x^12 and 8^12), which means it's easier to get -Wall clean without having to put :: Int annotations everywhere.

I agree that is a benefit (making it easier to avoid warnings), but in my opinion it is a tiny benefit.

Let me guess - you don't use -Wall. :-) Warnings are not the problem, warnings point to a problem. The problem here is, that the compiler has to guess a type, because it cannot be infered from other operands.

The inverse proposal has the same benefit, and doesn't require a change to GHC: just add intPower to your own code, and use it wherever you want. If you are unhappy with the idea of using intPower, perhaps you understand why I'm unhappy with the prospect of having to use genericPower.

Question: How often did you need the genericity of Haskell 98 (^) ? That is, how often do you call (^) with a non-constant exponent and how often is the exponent constant? If I have (^) with variable exponents too often in the code, I suspect that I missed some optimizations like (iterate (x*) 1). I have done (semi-automatically) some statistics on my mathematical stuff in Haskell, namely http://darcs.haskell.org/htam/src (^^) used with exponents (1-j) (n2-1) n pred n (^) used with variable exponents i j m n n n n degree xs degree xs degree ys (n2-1) mod n 2 mod (p+1) 2 (^) used with constant exponents 2: 169 times 3: 31 times 4: 9 times 5: 10 times 6: 3 times 7: 2 times 8: 1 times 9: 1 times If I search for '::Int', the most results are exponents of (^), others are from enumerations like [(0::Int)..].