context/README.md

context

A context manager protocol for zepto.

Installation

zeps install hellerve/context

Context Managers?

Context managers provide the programmer with an easy way to work with resources that need management, i.e. explicit cleanup and/or deletion. Consider files for example: if we want to use them, we need to open them, work with them and then close them again. Context managers provide you with a context in which a file will be open, managing the closing itself when you are done.

An example:

; reading the first line of a file, without a context manager
(define file (open-input-file "myfile.txt"))
(write (read-line file))
(close-input-file file)

; the same, this time with a context manager
(with (open-input-file "myfile.txt") file
  (write (read-line file)))

Usage

The example above already showcases the most important function for users, with. It takes a value, a name to bind it to and a context in which this name should be defined.

(with some-resource some-name
  (do-something some-name)
  (do-another-thing some-name))

The library also exposes a protocol context-manager, comprised of a function teardown which will clean a resource up after use.

Use it like so:

(defimpl context-manager my-resource?
         ((teardown (lambda (resource)
                      (begin
                        (cleanup-my-resource resource)
                        (delete-my-resource resource))))))
```

That's all, folks!

This library comes bundled with a context manager for files and sockets.

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Have fun!