A record storing a Function and its Function Environment in a function such that:
- Subsequent calls to the same closure can have the same Function Environment!
- Functions can oftentimes pass their Function Environment to outer closure
Languages that implement closures often can also handle inner-closures, similar to LISP. Often very expensive to implement memory-wise.
Inner vs Outer Closure
Inner Closure
The region within a function
Outer Closure
The region surrounding a function