• Puming (8/8) Aug 30 2014 Clojure is introducing a new way of composing functions (reducers
• Philippe Sigaud via Digitalmars-d (24/25) Aug 31 2014 Hickey's original announcement is also interesting to read. Elegant, as ...

"Puming" <zhaopuming gmail.com> writes:

Clojure is introducing a new way of composing functions (reducers 
this time), called transducers. It looks similar to 
composition/binding of functions, but somehow different. My 
functional-fu is not that deep to understand the statement 
"transducers are as fundamental as function composition" but it 
seems quite interesting. What is D's attitude toward this concept?

Here is a blog I read about transducers today:

http://thecomputersarewinning.com/post/Transducers-Are-Fundamental/

Philippe Sigaud via Digitalmars-d <digitalmars-d puremagic.com> writes:

 What is D's attitude toward this concept?

Hickey's original announcement is also interesting to read. Elegant, as always.

It seems to me that ranges and range algorithms in D already permit
this composition of actions, without the creation of intermediate
structures:

import std.algorithm;
import std.functional: pipe;

alias incsum = pipe!(
                map!(x => x+1),
                reduce!((x,y) => x+y)
                );

alias filtermap = pipe!(
                   filter!(x => x%2==0),
                   map!(x => x+1)
                  );

alias mapfilter = pipe!(
                    map!(x => x+1),
                   filter!(x => x%2==0)
                  );

void main() {
    auto sequence = iota(10);
    writeln(incsum(sequence)); // 55
    writeln(filtermap(sequence)); // [1, 3, 5, 7, 9]
    writeln(mapfilter(sequence)); // [2, 4, 6, 8, 10]
}