On Wed, Aug 24, 2011 at 6:41 PM, Joshua Juran <jjuran@gmail.com> wrote:
On Aug 24, 2011, at 1:38 PM, Dave Abrahams wrote:
I mean this, for a ternary function f:
f(x) => doesn't call f f(x)(y) => doesn't call f f(x)(y)(z) => calls f
That last step looks asymmetric to me.
In a lazy language, f(x)(y)(z) *doesn't* call f... until you actually use the result for something... which is more consistent-looking.
I suppose the symmetrical non-lazy version looks like:
f(x) => doesn't call f f(x)(y) => doesn't call f f(x)(y)(z) => doesn't call f f(x)(y)(z)() => calls f
What about using [] for currying and () for calling?
f[x] => returns binary function f[x][y] => returns unary function f[x][y][z] => returns nullary function
All of these have the same effect:
f(x, y, z) f[x](y, z) f[x][y](z) f[x][y][z]()
My vote is to Keep It Simple: Use a "curry" function to "curry-fy" an immediate (i.e., normal C++) function F, with each application of "(arg)" directly either (a) evaluating F with the current argument together with all the previously curried argument (if possible); or (b) currying the argument. This was Eric's original proposal, as far as I could tell. Just add to this a family of "curryN" ("curry2", "curry3", ...) functions that "curry-fy" an immediate function *and* fix its arity to N; thus, the first N-1 "(arg)" applications would curry the argument. - Jeff