Dear all,

Is it possible in Julia to define a C++-like operator() for its 
"struct-like" composite types (defined with type....end)? Thanks to such a 
method, one may treat an object as a function.

Here's a GitHub gist illustrating what I'm trying to achieve: 
https://gist.github.com/gagolews/9206364

In other words, I'd like to create a function which has some associated 
(deep copied) objects with it, by calling new_function = 
create_function(data) and such that new_function does not rely on dataanymore 
(at least from its caller/user perspective). I tried to play with 
Julia's macros, but I'm quite sure it's not the case here.

My inspiration is R's approxfun() which returns a function object that 
interpolates (linearly) a given set of points in 2D. I'm trying to develop 
a similar tool in Julia, but I cannot move on because of this issue.

> (x <- seq(0, 1, length.out=10))
 [1] 0.0000000 0.1111111 0.2222222 0.3333333 0.4444444 0.5555556 0.6666667
 [8] 0.7777778 0.8888889 1.0000000
> (y <- x^2)
 [1] 0.00000000 0.01234568 0.04938272 0.11111111 0.19753086 0.30864198
 [7] 0.44444444 0.60493827 0.79012346 1.00000000
> f <- approxfun(x, y)
> f(0.35)
[1] 0.1240741
> y <- sqrt(x)
> f(0.35) # no change (y is stored "within" f)
[1] 0.1240741
> # more precisely it is a new environment ("hash table")
> # ASSOCIATED with the function
> ls(envir=environment(f))
[1] "f"      "method" "x"      "y"      "yleft"  "yright"
> f # one source code, but operates on different data
function (v) 
.approxfun(x, y, v, method, yleft, yright, f)
<bytecode: 0x2ff5fb8>
<environment: 0x320a7d0>

Anybody?

Best regards,
Marek Gagolewski
http://gagolewski.rexamine.com

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