Pipes

Motivation

Sometimes when writing code, you have a situation such as this:

fun int incr(int i) {
  return i + 1;
}

<<< incr(incr(incr(incr(1)))) >>>;

This code looks rather unappealing due to the nested functions. Instead, you can use pipes!

Usage

Instead of nesting functions over and over again, you can pipe the functions in a nice line.

fun int incr(int i) {
  return i + 1;
}

<<< 1 => incr => incr => incr => incr >>>;

As you can see, the 1 is piped into the incr function, and the result of that is piped into the incr function, and so on.

Multiple arguments

Piping works a little differently if your function has multiple arguments. If a function has multiple arguments, there are two ways to pipe.

First off, you can pipe all arguments directly.

fun int add(int i, int j) {
  return i + j;
}

<<< (1, 2) => add >>>;

Second off, you can pipe arguments one at a time.

fun int add(int i, int j) {
  return i + j;
}

<<< 1 => add(_, 2) >>>;
<<< 2 => add(1, _) >>>;

The underscore determines where the piped argument goes. In the first line, 1 goes into the first argument, whereas in the second line, 2 goes into the second argument.

You can also have multiple underscores.

fun int add3(int i, int j, int k) {
  return i + j + k;
}

<<< (1, 3) => add3(_, 2, _) >>>;

The arguments go into their respective underscores. In this case, 1 goes into the first argument and 3 goes into the third.