CSC/ECE 517 Fall 2011/ch1 1d sr

Wiki Chapter: CSC/ECE 517 Fall 2011/ch1 1d sr

Closures

What are Closures

Let us try to define what a closure as a programming construct means.

A Closure is basically a function or a method (or a block, in the context of ruby) that has the following two properties -

• One can pass it around like an object or as a value parameter to other functions/methods/blocks

• It takes the snapshot and effectively "remembers" the values of all the variables that were in scope when the function was created and it is because of this property that it is able to access those variables when it is called even though they may no longer be in scope. 5

In order for a programming language to be able to support closures, it must support the notion of "first class functions." A first class function can be treated like an object in that you can pass it around as parameter or you can store it in collections. [6]

Since a closure can be passed around as a value before calling it, it can be called in a completely different scope than the one in which it was created and it is because of this that it needs to retain the knowledge of the lexical environment in which it was defined. [4]

References

1. Matz discussion on Closures

2. Closures in C++

3. Closures in C

4. Closures in Java

External Links

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