On 12/26/2012 11:09 PM, Walter Bright wrote:
On 12/26/2012 8:34 AM, Russel Winder wrote:
But isn't that the whole point, in functional programming there is only
immutable data. Thus a programming language that allows mutable data
cannot really be said to be usable for functional programming style.
In D, you can declare immutable data and immutable data structures. This
makes it usable for FP style (along with checkable function purity).
immutable and const are incompatible with lazy evaluation. Lazy
evaluation is not strictly necessary for FP, but it makes code a lot
more expressive. (D ranges are lazy.)
But D also does something I think is fairly unique. A function can be
pure, but inside that function, mutation is allowed as long as that
mutation does not "leak" outside of the function. A pure function with
immutable parameters does completely specify the function in its
signature. What happens inside the function is not relevant, it is not
necessary that locals be immutable.
Haskell has this.
