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Add more documentation to the loop macro.

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Calvin Rose 2018-11-18 09:55:31 -05:00
parent 3d5c8e3584
commit 7ff74c8ac9
1 changed files with 25 additions and 3 deletions
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src/core/core.janet
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@ -258,7 +258,27 @@
(tuple 'if $fi $fi (aux (+ 1 i))))))))) 0))) (tuple 'if $fi $fi (aux (+ 1 i))))))))) 0)))
(defmacro loop (defmacro loop
"A general purpose loop macro." "A general purpose loop macro.
The head of the loop shoud be a tuple that contains a sequence of
either bindings or conditionals. A binding is a sequence of three values
that define someting to loop over. They are formatted like:\n\n
\tbinding :verb object/expression\n\n
Where binding is a binding as passed to def, :verb is one of a set of keywords,
and object is any janet expression. The available verbs are:\n\n
\t:iterate - repeatedly evaluate and bind to the expression while it is truthy.\n
\t:range - loop over a range. The object should be two element tuple with a start
and end value. The range is half open, [start, end).\n
\t:keys - Iterate over the keys in a data structure.\n
\t:in - Iterate over the values in an indexed data structure or byte sequence.\n\n
loop also accepts conditionals to refine the looping further. Conditionals are of
the form:\n\n
\t:modifier argument\n\n
where :modifier is one of a set of keywords, and argument is keyword dependent.
:modifier can be one of:\n\n
\t:while expression - breaks from the loop if expression is falsey.\n
\t:let bindings - defines bindings inside the loop as passed to the let macro.\n
\t:when condition - only evaluates the loop body when condition is true.\n\n
The loop macro always evaluates to nil."
[head & body] [head & body]
(def len (length head)) (def len (length head))
(defn doone (defn doone
@ -334,7 +354,8 @@
(doone 0 nil)) (doone 0 nil))
(defmacro fora (defmacro fora
"Similar to loop, but accumulates the loop body into an array and returns that." "Similar to loop, but accumulates the loop body into an array and returns that.
See loop for details."
[head & body] [head & body]
(def $accum (gensym)) (def $accum (gensym))
(tuple 'do (tuple 'do
@ -345,7 +366,8 @@
$accum)) $accum))
(defmacro for (defmacro for
"Similar to loop, but accumulates the loop body into a tuple and returns that." "Similar to loop, but accumulates the loop body into a tuple and returns that.
See loop for details."
[head & body] [head & body]
(def $accum (gensym)) (def $accum (gensym))
(tuple 'do (tuple 'do