D言語でカリー化を用いて等差数列と等比数列書いてみた例(適当な例)

ap_gp.d

import std.stdio;

template curry(alias func){
  import std.algorithm, std.conv, std.range, std.traits;
  alias argsintuple = ParameterTypeTuple!func;

  immutable lambdaStr = (lamArgs =>
    (temp){
      foreach(i, e; argsintuple)
        temp ~= "(" ~ e.stringof ~ " " ~ lamArgs[i] ~ ") => ";

      return temp ~ "func(" ~ lamArgs.join(", ") ~ ")";
    }("")
  )(argsintuple.length.iota.map!(i => "arg" ~ i.to!string));

  enum curry = mixin(lambdaStr);
}

int ap(int a, int d, int n){
  return a + d * (n - 1);
}

int sumAp(int n, int delegate(int) f){
  return sumAp(n, f, 1);
}

int sumAp(int n, int delegate(int) f, int a){
  return n * (f(a) + f(n)) / 2;
}

int gp(int a, int r, int n){
  return a * r ^^ (n - 1);
}

int sumGp(int r, int n, int delegate(int) f){
  return r == 1 ? n * f(1) : (f(1) * (r^^n - 1)) / (r - 1);
}

void main(){
  auto apf = curry!ap;
  auto apg = apf(1)(4);
  foreach(i; 1..5)
    writeln(apg(i));
  writeln(sumAp(4, apg));
}