initial commit

.gitignore

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+/_build
+/deps
+erl_crash.dump
+*.ez

README.md

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+rebind
+======
+
+rebind parse transform for erlang
+
+Usage
+-----
+
+```erlang
+-module(test).
+-compile({parse_transform, rebind}).
+
+-export([sum/0]).
+
+sum() ->
+  State = 1,
+  rebind(State) = State + 1,
+  rebind(State) = State + 1,
+  rebind(State) = State + 1,
+  rebind(State) = State + 1,
+  State.
+```

mix.exs

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+defmodule Rebind.Mixfile do
+  use Mix.Project
+
+  def project do
+    [app: :rebind,
+     version: "0.1.0",
+     elixir: "~> 1.0",
+     deps: deps]
+  end
+
+  def application do
+    [applications: [:logger]]
+  end
+
+  defp deps do
+    [{:parse_trans, github: "uwiger/parse_trans"}]
+  end
+end

src/rebind.erl

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+-module(rebind).
+
+-export([parse_transform/2]).
+
+parse_transform(Forms, Options) ->
+  {Forms2, _} = parse_trans:transform(fun do_transform/4, #{}, Forms, Options),
+  parse_trans:revert(Forms2).
+
+do_transform(application,{call,_,{atom,_,rebind},[{var,Line,Name}]}, _Context, Acc) ->
+  Count = maps:get(Name, Acc, 0) + 1,
+  {rebind(Name, Line, Count), false, maps:put(Name, Count, Acc)};
+do_transform(variable,{var,Line,Name}, _Context, Acc) ->
+  {rebind(Name, Line, Acc), false, Acc};
+do_transform(match_expr, {match,Line,LH,RH}, Context, Acc) ->
+  %% reverse the recurse order
+  {RH2, Acc2} = traverse_match(RH,Acc,Context),
+  {LH2, Acc3} = traverse_match(LH,Acc2,Context),
+  {{match,Line,LH2,RH2}, false, Acc3};
+do_transform(_Type, Form, _Context, Acc) ->
+  {Form, true, Acc}.
+
+rebind(Name, Line, Acc) when is_map(Acc) ->
+  case maps:find(Name, Acc) of
+    error ->
+      {var, Line, Name};
+    {ok, Count} ->
+      rebind(Name, Line, Count)
+  end;
+rebind(Name, Line, Count) when is_integer(Count) ->
+  {var, Line, list_to_atom("_" ++ atom_to_list(Name) ++ "__REBIND__" ++ integer_to_list(Count))}.
+
+traverse_match(Side, Acc, Context) ->
+  {[Side2], Acc2} = parse_trans:do_transform(fun do_transform/4, Acc, [Side], Context),
+  [Out] = parse_trans:revert([Side2]),
+  {Out, Acc2}.