I agree that Num is the place to put this function, with a default implementation. In my mind it is a special combination of (+) and (*), which both live in Num as well. I dislike the name fma, as that is a three letter acronym with no meaning to people who don't do numeric programming. And by putting the function in Num the name would end up in the Prelude. For further bikeshedding: my proposal for a name would mulAdd. But fusedMulAdd or fusedMultiplyAdd would also be fine. Twan On 2015-04-30 00:19, Ken T Takusagawa wrote:
On Wed, 29 Apr 2015, Edward Kmett wrote:
Good point. If we wanted to we could push this all the way up to Num given the operations involved, and I could see that you could benefit from it there for types that have nothing to do with floating point, e.g. modular arithmetic could get away with using a single 'mod'.
I too advocate this go in Num. The place I anticipate seeing fma being used is in some polymorphic linear algebra library, and it is not uncommon (having recently done this myself) to do linear algebra on things that aren't RealFloat, e.g., Rational, Complex, or number-theoretic fields.
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