Stewart Gordon wrote:
Andrei Alexandrescu wrote:
Matti Niemenmaa wrote:
Haskell has three exponentiation operators in the standard library:
^, ^^, and **. They are for non-negative integral exponents, integral
exponents, and floating-point exponents respectively.
I wonder whether that's an illustration of the power or of the failure
of function overloading. (Seriously.)
I'm not sure either. I don't speak Haskell, but my guess is that ^ and
^^ were meant to cut out the confusion that would happen if Word32 ^
Word32 (what weird naming conventions Haskell has!) returned an integer
type but Int32 ^ Int32 returned a floating point type.
But why it needs yet another for floating-point exponents, I don't know.
Maybe Haskell supports only IFTI rather than true function overloading.
It's essentially because Haskell has separate type classes (kiiiinda
like D interfaces... I won't go into that topic) for integers,
fractional numbers, and floating-point numbers. In D the types of those
three operators could be something like:
anyinteger ^(anyinteger base, anyinteger exponent);
anyfractional ^^(anyfractional base, anyinteger exponent);
anyfloating **(anyfloating base, anyfloating exponent);
A noteworthy fractional is the Rational type, a ratio of two integral
values. Note that 0.5 is a valid Rational: it's 1/2. Note, still, that
0.5 ** 0.5 is no longer a valid Rational: it's the square root of 1/2.
This is why ^^ is separate: fractionals can be safely raised to integer
exponents, but if you take a fractional and raise it to a fractional
power, you might not get a fractional back.
