Generators

Generators

Table of Contents

• Syntax
• Semantics
• Errors

Table of Contents

• Syntax
• Semantics
• Errors

Generators are functions that use yield to produce a sequence of values. Calling a generator executes the function immediately and returns a list of the yielded values.

Syntax

fn range(n) {
  let i = 0;
  while (i < n) {
    yield i;
    i += 1;
  }
}

let xs = range(4); // [0, 1, 2, 3]

Semantics

• yield expr appends a value to the generator result list.
• A function becomes a generator if it contains any yield statement.
• Calling a generator returns a list of all yielded values.
• return values in a generator are ignored (the list is returned instead).

Errors

Using yield outside of a generator is a runtime error.