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# loop.el --- friendly imperative loop structures for Emacs lisp
Emacs lisp is missing loop structures familiar to users of newer
languages. This library adds a selection of popular loop structures
as well as break and continue.
loop.el also has full unit tests.
<!-- markdown-toc start - Don't edit this section. Run M-x markdown-toc-generate-toc again -->
**Table of Contents**
- [loop.el --- friendly imperative loop structures for Emacs lisp](#loopel-----friendly-imperative-loop-structures-for-emacs-lisp)
- [Contents](#contents)
- [loop-while](#loop-while)
- [loop-do-while](#loop-do-while)
- [loop-until](#loop-until)
- [loop-for-each](#loop-for-each)
- [loop-for-each-line](#loop-for-each-line)
- [loop-break](#loop-break)
- [loop-continue](#loop-continue)
- [Alternatives](#alternatives)
- [Changelog](#changelog)
- [Running the tests](#running-the-tests)
<!-- markdown-toc end -->
## Contents
### loop-while
Repeatedly evaluate BODY while CONDITION is non-nil.
`loop-while` `(condition body...)`
Example:
``` lisp
(let ((x 0)
(sum 0))
;; sum the numbers 0 to 9
(loop-while (< x 10)
(setq sum (+ sum x))
(setq x (1+ x))))
```
### loop-do-while
Evaluate BODY, then repeatedly BODY while CONDITION is non-nil.
`loop-do-while` `(condition body...)`
Example:
``` lisp
(let ((x 0)
(sum 0))
;; our condition is false on the first iteration
(loop-do-while (and (> x 0) (< x 10))
(setq sum (+ sum x))
(setq x (1+ x))))
```
### loop-until
Repeatedly evaluate BODY until CONDITION is non-nil.
`loop-until` `(condition body...)`
Example:
``` lisp
(let ((x 0)
(sum 0))
;; sum the numbers 0 to 9
(loop-until (= x 10)
(setq sum (+ sum x))
(setq x (1+ x))))
```
### loop-for-each
For every item in LIST, evaluate BODY with VAR bound to that item.
* `loop-for-each` `(var list body...)`
Example:
``` lisp
(let ((sum 0))
(loop-for-each x (list 1 2 3 4 5 6 7 8 9)
(setq sum (+ sum x))))
```
### loop-for-each-line
For every line in the buffer, put point at the start of the line and
execute BODY.
* `loop-for-each-loop` `(body...)`
Example:
``` lisp
;; Count headings in a markdown buffer.
(let ((heading-count 0))
(loop-for-each-line
(when (looking-at "#")
(setq heading-count (+ heading 1))))
```
### loop-break
Terminate evaluation of a `loop-while`, `loop-do-while`,
`loop-for-each`, or `loop-for-each-line` block. If there are nested
loops, breaks out of the innermost loop.
`loop-break` `()`
Example:
``` lisp
(let ((sum 0))
;; sum the numbers 1 to 5
(loop-for-each x (list 1 2 3 4 5 6 7 8 9)
(setq sum (+ sum x))
(when (= x 5)
(loop-break))))
```
### loop-continue
Skip the rest of the current `loop-while`, `loop-do-while`, or
`loop-for-each` block and continue to the next iteration. If there
are nested loops, applies to the innermost loop.
`loop-continue` `()`
Example:
``` lisp
(let ((sum 0))
;; sum the numbers 1, 3, 4, 5
(loop-for-each x (list 1 2 3 4 5)
(when (= x 2)
(loop-continue))
(setq sum (+ sum x))))
```
## Alternatives
* `while` and `dolist` are built-in loop structures
* The `cl-loop` macro in `cl-lib`
* `-each` in [dash.el](https://github.com/magnars/dash.el)
## Changelog
* v1.3 `loop-for-each-line` now works even if point moves
around. Inside `loop-for-each-line`, `it` is now set to the current
line. Added `loop-return`.
* v1.2 Added `loop-for-each-line`. Also added edebug support, so you
can step through loops in loop.el.
* v1.1 Added `loop-continue`
* v1.0 `loop-for-each` now takes three arguments: `(VAR LIST BODY...)`
* v0.3 Added `loop-until`
* v0.2 Basic working implementation
## Running the tests
M-x loop-run-tests
|
