481 lines
14 KiB
Erlang
481 lines
14 KiB
Erlang
%%% The contents of this file are subject to the Erlang Public License,
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%%% Version 1.0, (the "License"); you may not use this file except in
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%%% compliance with the License. You may obtain a copy of the License at
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%%% http://www.erlang.org/license/EPL1_0.txt
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%%%
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%%% Software distributed under the License is distributed on an "AS IS"
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%%% basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
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%%% the License for the specific language governing rights and limitations
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%%% under the License.
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%%%
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%%% The Original Code is exprecs-0.2.
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%%%
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%%% The Initial Developer of the Original Code is Ericsson AB.
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%%% Portions created by Ericsson are Copyright (C), 2006, Ericsson AB.
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%%% All Rights Reserved.
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%%%
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%%% Contributor(s): ______________________________________.
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%%%-------------------------------------------------------------------
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%%% File : exprecs.erl
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%%% @author : Ulf Wiger <ulf.wiger@ericsson.com>
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%%% @end
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%%% Description :
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%%%
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%%% Created : 13 Feb 2006 by Ulf Wiger <ulf.wiger@ericsson.com>
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%%%-------------------------------------------------------------------
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%%% @doc Parse transform for generating record access functions
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%%% <p>This parse transform can be used to reduce compile-time
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%%% dependencies in large systems.</p>
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%%% <p>In the old days, before records, Erlang programmers often wrote
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%%% access functions for tuple data. This was tedious and error-prone.
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%%% The record syntax made this easier, but since records were implemented
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%%% fully in the pre-processor, a nasty compile-time dependency was
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%%% introduced.</p>
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%%% <p>This module automates the generation of access functions for
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%%% records. While this method cannot fully replace the utility of
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%%% pattern matching, it does allow a fair bit of functionality on
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%%% records without the need for compile-time dependencies.</p>
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%%% <p>Whenever record definitions need to be exported from a module,
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%%% inserting a compiler attribute,
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%%% <code>export_records([RecName|...])</code> causes this transform
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%%% to lay out access functions for the exported records:</p>
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%%%
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%%% <pre>
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%%% -record(a, {a, b, c}).
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%%% -export_records([a]).
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%%% -export(['#info-'/2,
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%%% '#get-'/2, '#set-'/2,
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%%% '#new-a'/0, '#new-a'/1,
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%%% '#get-a'/2, '#set-a'/2,
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%%% '#info-a'/1]).
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%%%
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%%% '#info-'(Info, Rec) when is_record(Rec, a) ->
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%%% '#info-a'(Info).
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%%%
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%%% '#get-'(Attrs, Rec) when is_record(Rec, a) ->
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%%% '#get-a'(Attrs, Rec).
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%%%
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%%% '#set-'(Attrs, Rec) when is_record(Rec, a) ->
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%%% '#set-a'(Attrs, Rec).
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%%%
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%%% '#new-a'() -> #a{}.
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%%% '#new-a'(Vals) -> '#set-a'(Vals, #a{}).
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%%%
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%%% '#get-a'(Attrs, R) when is_list(Attrs) ->
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%%% ['#get-a'(A, R) || A <- Attrs];
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%%% '#get-a'(a, R) -> R#a.a;
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%%% '#get-a'(b, R) -> R#a.b;
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%%% '#get-a'(c, R) -> R#a.c.
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%%%
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%%% '#set-a'(Vals, Rec) ->
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%%% F = fun ([], R, _F1) -> R;
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%%% ([{a, V} | T], R, F1) -> F1(T, R#a{a = V}, F1);
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%%% ([{b, V} | T], R, F1) -> F1(T, R#a{b = V}, F1);
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%%% ([{c, V} | T], R, F1) -> F1(T, R#a{c = V}, F1)
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%%% end,
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%%% F(Vals, Rec, F).
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%%%
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%%% '#info-a'(size) -> record_info(size, a);
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%%% '#info-a'(fields) -> record_info(fields, a).
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%%% </pre>
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%%% <p>The generated accessor functions are:</p>
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%%% <table border="1">
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%%% <tr><td><code>'#new-R'() -> #R{}</code></td>
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%%% <td>Instantiates a new record of type `R'.</td></tr>
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%%% <tr><td><code>'#new-R'(Data) -> #R{}</code></td>
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%%% <td>Exactly equivalent to calling
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%%% <code>'#set-R'(Data,'#new-R'())</code></td></tr>
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%%% <tr><td><code>'#info-R'(Info) -><br/>
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%%%   [FldName]<br/>
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%%% Info :: fields | size</code></td>
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%%% <td>Equivalent to `record_info(fields, R)' for the
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%%% given record type R.</td></tr>
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%%% <tr><td><code>'#info-'(Info, Rec) -><br/>
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%%%   [FldName]</code></td>
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%%% <td>Detects the record type of `Rec', and calls the corresponding
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%%% <code>'#info-R'/1</code> function.</td></tr>
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%%% <tr><td><code>'#get-R'(A, Rec) -><br/>
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%%%   Value | [Value]</code></td>
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%%% <td>Returns the value (if `A' is an atom) of the given field,
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%%% in `Rec' (which must be a record of type `R'),
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%%% or a list of values (if `A' is a list of atoms).</td></tr>
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%%% <tr><td><code>'#get-'(A, Rec) -><br/>
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%%%   Value | [Value]</code></td>
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%%% <td>Detects the record type of `Rec' and calls the corresponding
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%%% <code>'#get-R'(A, Rec)</code> function.</td></tr>
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%%% <tr><td><code>'#set-R'(Data, Rec) -><br/>
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%%%   Data | [{Attr::atom(), Value}]</code></td>
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%%% <td>Takes a list of `{Attr,Value}' tuples and sets the corresponding
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%%% attributes in the record `Rec' (which must be of type `R').
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%%% Each `Attr' in the list must correspond to an actual attribute
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%%% in the record `R'.</td></tr>
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%%% <tr><td><code>'#set-'(Data, Rec) -><br/>
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%%%   Value | [Value]</code></td>
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%%% <td>Detects the record type of `Rec' and calls the corresponding
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%%% <code>'#set-R'(Data, Rec)</code> function.</td></tr>
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%%% </table>
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%%% @end
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-module(exprecs).
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-export([parse_transform/2,
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format_error/1,
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transform/3,
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context/2]).
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-record(context, {module,
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function,
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arity}).
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-record(pass1, {exports = [],
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generated = false,
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records = []}).
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-define(HERE, {?MODULE, ?LINE}).
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-define(ERROR(R, F, I),
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begin
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rpt_error(R, F, I),
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throw({error,get_pos(I),{unknown,R}})
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end).
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get_pos(I) ->
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case proplists:get_value(form, I) of
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undefined ->
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0;
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Form ->
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erl_syntax:get_pos(Form)
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end.
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parse_transform(Forms, Options) ->
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[File|_] = [F || {attribute,_,file,{F,_}} <- Forms],
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try do_transform(Forms, Options) of
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Res ->
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%% io:format("Res = ~p~n", [Res]),
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Res
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catch
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throw:{error, Ln, What} ->
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{error, [{File, [{Ln, ?MODULE, What}]}], []}
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end.
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do_transform(Forms, _Options) ->
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%%
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%% 1st pass - collect record info
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%%
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Fun1 =
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fun(attribute, {attribute,_L,record,RecDef}=Form, _Ctxt, Acc) ->
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Recs0 = Acc#pass1.records,
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{Form, false, Acc#pass1{records = [RecDef|Recs0]}};
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(attribute, {attribute,_L,export_records, E}=Form, _Ctxt, Acc) ->
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Exports0 = Acc#pass1.exports,
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NewExports = Exports0 ++ E,
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{Form, false, Acc#pass1{exports = NewExports}};
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(_Type, Form, _Context, Acc) ->
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{Form, false, Acc}
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end,
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{Forms1, Acc1} = pass(Forms, Fun1, _Acc = #pass1{}),
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%%
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%% 2nd pass - generate accessor functions
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%%
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Fun2 =
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fun(attribute, {attribute,L,export_records,Es} = Form, _Ctxt,
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#pass1{exports = [_|_] = Es} = Acc) ->
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Exports = [{list_to_atom(fname_prefix(info)), 2},
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{list_to_atom(fname_prefix(get)), 2},
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{list_to_atom(fname_prefix(set)), 2} |
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lists:concat(
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lists:map(
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fun(Rec) ->
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FNew = fname(new, Rec),
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[{FNew, 0}, {FNew,1},
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{fname(get, Rec), 2},
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{fname(set, Rec), 2},
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{fname(info, Rec), 1}]
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end, Es))],
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{[],
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Form,
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[{attribute,L,export,Exports}],
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false, Acc};
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(function, Form, _Ctxt, #pass1{exports = [_|_],
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generated = false} = Acc) ->
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%% Layout record funs before first function
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L = element(2, Form),
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Funs = generate_accessors(L, Acc),
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{Funs, Form, [], false, Acc#pass1{generated = true}};
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(_Type, Form, _Ctxt, Acc) ->
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{Form, false, Acc}
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end,
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{Forms2, Acc2} = pass(Forms1, Fun2, Acc1),
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case Acc2#pass1.generated of
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true ->
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Forms2;
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false ->
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case Acc2#pass1.exports of
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[] ->
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Forms2;
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[_|_] ->
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[{eof,Last}|RevForms] = lists:reverse(Forms2),
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[{function, NewLast, _, _, _}|_] = RevAs =
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lists:reverse(generate_accessors(Last, Acc2)),
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lists:reverse([{eof, NewLast+1} | RevAs] ++ RevForms)
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end
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end.
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pass(Forms, Fun, Acc) ->
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{NewTree, NewAcc} = transform(Forms, Fun, Acc),
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NewForms = [erl_syntax:revert(T) || T <- lists:flatten(NewTree)],
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{NewForms, NewAcc}.
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generate_accessors(L, Acc) ->
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[f_info(Acc, L),
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f_get(Acc, L),
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f_set(Acc, L) |
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lists:concat(
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lists:map(
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fun(Rname) ->
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Fields = get_flds(Rname, Acc),
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[f_new_0(Rname, L),
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f_new_1(Rname, L),
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f_get_2(Rname, Fields, L),
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f_set_2(Rname, Fields, L),
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f_info_1(Rname, L)]
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end, Acc#pass1.exports))].
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get_flds(Rname, #pass1{records = Rs}) ->
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{value, {_, Flds}} = lists:keysearch(Rname, 1, Rs),
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lists:map(
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fun({record_field,_, {atom,_,N}}) -> N;
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({record_field,_, {atom,_,N}, _}) -> N
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end, Flds).
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fname_prefix(Op) ->
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case Op of
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new -> "#new-";
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get -> "#get-";
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set -> "#set-";
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info -> "#info-"
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end.
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fname(Op, Rname) ->
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Prefix = fname_prefix(Op),
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list_to_atom(Prefix ++ atom_to_list(Rname)).
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%%% Accessor functions
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%%%
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f_new_0(Rname, L) ->
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{function, L, fname(new, Rname), 0,
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[{clause, L, [], [],
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[{record, L, Rname, []}]}]}.
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f_new_1(Rname, L) ->
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{function, L, fname(new, Rname), 1,
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[{clause, L, [{var, L, 'Vals'}], [],
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[{call, L, {atom, L, fname(set, Rname)},
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[{var, L, 'Vals'},
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{record, L, Rname, []}
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]}]
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}]}.
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f_set_2(Rname, Flds, L) ->
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{function, L, fname(set, Rname), 2,
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[{clause, L, [{var, L, 'Vals'}, {var, L, 'Rec'}], [],
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[{match, L, {var, L, 'F'},
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{'fun', L,
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{clauses,
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[{clause, L, [{nil,L},
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{var,L,'R'},
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{var,L,'_F1'}],
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[],
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[{var, L, 'R'}]} |
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[{clause, L,
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[{cons, L, {tuple, L, [{atom, L, Attr},
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{var, L, 'V'}]},
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{var, L, 'T'}},
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{var, L, 'R'},
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{var, L, 'F1'}],
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[],
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[{call, L, {var, L, 'F1'},
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[{var,L,'T'},
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{record, L, {var,L,'R'}, Rname,
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[{record_field, L,
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{atom, L, Attr},
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{var, L, 'V'}}]},
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{var, L, 'F1'}]}]} || Attr <- Flds]]}}},
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{call, L, {var, L, 'F'}, [{var, L, 'Vals'},
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{var, L, 'Rec'},
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{var, L, 'F'}]}]}]}.
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f_get_2(Rname, Flds, L) ->
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FName = fname(get, Rname),
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{function, L, FName, 2,
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[{clause, L, [{var, L, 'Attrs'}, {var, L, 'R'}],
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[[{call, L, {atom, L, is_list}, [{var, L, 'Attrs'}]}]],
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[{lc, L, {call, L, {atom, L, FName}, [{var, L, 'A'}, {var, L, 'R'}]},
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[{generate, L, {var, L, 'A'}, {var, L, 'Attrs'}}]}]
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} |
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[{clause, L, [{atom, L, Attr}, {var, L, 'R'}], [],
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[{record_field, L, {var, L, 'R'}, Rname, {atom, L, Attr}}]} ||
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Attr <- Flds]]
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}.
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f_info(Acc, L) ->
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Fname = list_to_atom(fname_prefix(info)),
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{function, L, Fname, 2,
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[{clause, L,
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[{var, L, 'Info'}, {var, L, 'Rec'}],
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[[{call, L,
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{atom, L, is_record},
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[{var, L, 'Rec'}, {atom, L, R}]}]],
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[{call, L, {atom, L, fname(info, R)}, [{var, L, 'Info'}]}]} ||
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R <- Acc#pass1.exports]}.
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f_get(Acc, L) ->
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f_getset(get, Acc, L).
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f_set(Acc, L) ->
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f_getset(set, Acc, L).
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f_getset(Mode, Acc, L) when Mode == get; Mode == set ->
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Fname = list_to_atom(fname_prefix(Mode)),
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{function, L, Fname, 2,
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[{clause, L,
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[{var, L, 'Attrs'},
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{var, L, 'Rec'}],
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[[{call, L,
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{atom, L, is_record},
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[{var, L, 'Rec'}, {atom, L, R}]}]],
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[{call, L, {atom, L, fname(Mode, R)}, [{var, L, 'Attrs'},
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{var, L, 'Rec'}]}]} ||
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R <- Acc#pass1.exports]}.
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f_info_1(Rname, L) ->
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{function, L, fname(info, Rname), 1,
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[{clause, L, [{atom, L, fields}], [],
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[{call, L, {atom, L, record_info},
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[{atom, L, fields}, {atom, L, Rname}]}]
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},
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{clause, L, [{atom, L, size}], [],
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[{call, L, {atom, L, record_info},
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[{atom, L, size}, {atom, L, Rname}]}]
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}]}.
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%%% ========== generic parse_transform stuff ==============
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context(module, #context{module = M} ) -> M;
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context(function, #context{function = F}) -> F;
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context(arity, #context{arity = A} ) -> A.
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transform(Forms, F, Acc) ->
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case [{L,M} || {attribute, L, module, M} <- Forms] of
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[{_,Module}] ->
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transform(Forms, F, #context{module = Module}, Acc);
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[] ->
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?ERROR(missing_module_attribute, ?HERE, []);
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[_|_] = Multiple ->
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?ERROR(multiple_module_attributes, ?HERE,
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[{L,{module,M}} || {L,M} <- Multiple])
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end.
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transform(Forms, F, Context, Acc) ->
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F1 =
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fun(Form, Acc0) ->
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Type = erl_syntax:type(Form),
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{Before1, Form1, After1, Recurse, Acc1} =
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try F(Type, Form, Context, Acc0) of
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{F1, Rec1, A1} ->
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{[], F1, [], Rec1, A1};
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{_Be1, _F1, _Af1, _Rec1, _Ac1} = Res1 ->
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Res1
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catch
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error:Reason ->
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?ERROR(Reason,
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?HERE,
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[{type, Type},
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{context, Context},
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{acc, Acc},
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{form, Form}])
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end,
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if Recurse == true ->
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case erl_syntax:subtrees(Form1) of
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[] ->
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{Before1, Form1, After1, Acc1};
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ListOfLists ->
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{NewListOfLists, NewAcc} =
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mapfoldl(
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fun(L, AccX) ->
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transform(
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L, F,
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new_context(
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Form1, Context), AccX)
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end, Acc1, ListOfLists),
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NewForm =
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erl_syntax:update_tree(
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Form, NewListOfLists),
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{Before1, NewForm, After1, NewAcc}
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end;
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true ->
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{Before1, Form1, After1, Acc1}
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end
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end,
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mapfoldl(F1, Acc, Forms).
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new_context(Form, Context0) ->
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case erl_syntax:type(Form) of
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function ->
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{Fun, Arity} =
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erl_syntax_lib:analyze_function(Form),
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Context0#context{function = Fun,
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arity = Arity};
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_ ->
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Context0
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end.
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%%% Slightly modified version of lists:mapfoldl/3
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%%% Here, F/2 is able to insert forms before and after the form
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%%% in question. The inserted forms are not transformed afterwards.
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mapfoldl(F, Accu0, [Hd|Tail]) ->
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{Before, Res, After, Accu1} =
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case F(Hd, Accu0) of
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{Be, _, Af, _} = Result when is_list(Be), is_list(Af) ->
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Result;
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{R1, A1} ->
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{[], R1, [], A1}
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end,
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{Rs, Accu2} = mapfoldl(F, Accu1, Tail),
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|
{Before ++ [Res| After ++ Rs], Accu2};
|
|
mapfoldl(F, Accu, []) when is_function(F, 2) -> {[], Accu}.
|
|
|
|
|
|
|
|
rpt_error(Reason, Fun, Info) ->
|
|
Fmt = lists:flatten(
|
|
["*** ERROR in parse_transform function:~n"
|
|
"*** Reason = ~p~n",
|
|
"*** Location: ~p~n",
|
|
["*** ~10w = ~p~n" || _ <- Info]]),
|
|
Args = [Reason, Fun |
|
|
lists:foldr(
|
|
fun({K,V}, Acc) ->
|
|
[K, V | Acc]
|
|
end, [], Info)],
|
|
io:format(Fmt, Args).
|
|
|
|
|
|
format_error({_Cat, Error}) ->
|
|
Error.
|