Version: 1.1.0

Closures

A closure is a function that captures names from the scope where it is created.

Essentials

• Capture by copy when you need a snapshot.
• A mutable capture requires the captured name to outlive every call.
• Closures can be passed to List methods and other higher-order functions.
• A closure that raises forces the caller to handle that error.
• Prefer a small named function when the capture list gets hard to read.

Example

def main():
    var base = 10
    fn add(n: Int) -> Int:
        return n + base
    print(add(5))

Keep in mind

Capturing a reference to a local and returning the closure is rejected when the local would die first.