Closure

Functions are closures that capture their lexical environment and are first class. They can be passed around like any other variable. For example:

fn adder(x) {
   fn (y) { x + y }
}

define add2 = adder(2);
define add3 = adder(3);

add2(3); // 5
add3(3); // 6

The inner anonymous function returned by adder captures the argument value of x and when later invoked adds that to its argument y.

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