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Merged
merged 2 commits into from
Apr 25, 2021
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Add documentation for Macro.prewalk/2 #10951

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b34d78e
Add documentation for `Macro.prewalk/2`
iaguirre88 Apr 24, 2021
1c9412c
Update lib/elixir/lib/macro.ex
josevalim Apr 25, 2021
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17 changes: 17 additions & 0 deletions lib/elixir/lib/macro.ex
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Expand Up @@ -490,6 +490,23 @@ defmodule Macro do

@doc """
Performs a depth-first, pre-order traversal of quoted expressions.

Returns a new ast where each node is the result of invoking `fun` on each
corresponding node of `ast`.

## Examples

iex> ast = quote do: 5 + 3 * 7
iex> new_ast = Macro.prewalk(ast, fn
...> {:+, meta, children} -> {:*, meta, children}
...> {:*, meta, children} -> {:+, meta, children}
...> other -> other
...> end)
iex> Code.eval_quoted(ast)
{26, []}
iex> Code.eval_quoted(new_ast)
{50, []}

"""
@spec prewalk(t, (t -> t)) :: t
def prewalk(ast, fun) when is_function(fun, 1) do
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