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%%
%% %CopyrightBegin%
%%
%% Copyright Ericsson AB 2000-2016. All Rights Reserved.
%%
%% Licensed under the Apache License, Version 2.0 (the "License");
%% you may not use this file except in compliance with the License.
%% You may obtain a copy of the License at
%%
%% http://www.apache.org/licenses/LICENSE-2.0
%%
%% Unless required by applicable law or agreed to in writing, software
%% distributed under the License is distributed on an "AS IS" BASIS,
%% WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
%% See the License for the specific language governing permissions and
%% limitations under the License.
%%
%% %CopyrightEnd%
%%
%% Purpose: Core Erlang abstract syntax functions.
-module(core_lib).
-export([make_values/1]).
-export([is_var_used/2]).
-include("core_parse.hrl").
%% Make a suitable values structure, expr or values, depending on Expr.
-spec make_values([cerl:cerl()] | cerl:cerl()) -> cerl:cerl().
make_values([E]) -> E;
make_values([H|_]=Es) -> #c_values{anno=cerl:get_ann(H),es=Es};
make_values([]) -> #c_values{es=[]};
make_values(E) -> E.
%% Test if the variable VarName is used in Expr.
-spec is_var_used(cerl:var_name(), cerl:cerl()) -> boolean().
is_var_used(V, B) -> vu_expr(V, B).
vu_expr(V, #c_values{es=Es}) ->
vu_expr_list(V, Es);
vu_expr(V, #c_var{name=V2}) -> V =:= V2;
vu_expr(V, #c_alias{var=V2,pat=Pat}) ->
%% XXX Must handle aliases in expressions because of sys_core_fold:kill_types/2,
%% that uses a pattern as if it was an expression.
V =:= V2 orelse vu_expr(V, Pat);
vu_expr(_, #c_literal{}) -> false;
vu_expr(V, #c_cons{hd=H,tl=T}) ->
vu_expr(V, H) orelse vu_expr(V, T);
vu_expr(V, #c_tuple{es=Es}) ->
vu_expr_list(V, Es);
vu_expr(V, #c_map{arg=M,es=Es}) ->
vu_expr(V, M) orelse vu_expr_list(V, Es);
vu_expr(V, #c_map_pair{key=Key,val=Val}) ->
vu_expr_list(V, [Key,Val]);
vu_expr(V, #c_binary{segments=Ss}) ->
vu_seg_list(V, Ss);
vu_expr(V, #c_fun{vars=Vs,body=B}) ->
%% Variables in fun shadow previous variables
case vu_var_list(V, Vs) of
true -> false;
false -> vu_expr(V, B)
end;
vu_expr(V, #c_let{vars=Vs,arg=Arg,body=B}) ->
case vu_expr(V, Arg) of
true -> true;
false ->
%% Variables in let shadow previous variables.
case vu_var_list(V, Vs) of
true -> false;
false -> vu_expr(V, B)
end
end;
vu_expr(V, #c_letrec{defs=Fs,body=B}) ->
lists:any(fun ({_,Fb}) -> vu_expr(V, Fb) end, Fs) orelse vu_expr(V, B);
vu_expr(V, #c_seq{arg=Arg,body=B}) ->
vu_expr(V, Arg) orelse vu_expr(V, B);
vu_expr(V, #c_case{arg=Arg,clauses=Cs}) ->
vu_expr(V, Arg) orelse vu_clauses(V, Cs);
vu_expr(V, #c_receive{clauses=Cs,timeout=T,action=A}) ->
vu_clauses(V, Cs) orelse vu_expr(V, T) orelse vu_expr(V, A);
vu_expr(V, #c_apply{op=Op,args=As}) ->
vu_expr_list(V, [Op|As]);
vu_expr(V, #c_call{module=M,name=N,args=As}) ->
vu_expr_list(V, [M,N|As]);
vu_expr(V, #c_primop{args=As}) -> %Name is an atom
vu_expr_list(V, As);
vu_expr(V, #c_catch{body=B}) ->
vu_expr(V, B);
vu_expr(V, #c_try{arg=E,vars=Vs,body=B,evars=Evs,handler=H}) ->
case vu_expr(V, E) of
true -> true;
false ->
%% Variables shadow previous ones.
case case vu_var_list(V, Vs) of
true -> false;
false -> vu_expr(V, B)
end of
true -> true;
false ->
case vu_var_list(V, Evs) of
true -> false;
false -> vu_expr(V, H)
end
end
end.
vu_expr_list(V, Es) ->
lists:any(fun(E) -> vu_expr(V, E) end, Es).
vu_seg_list(V, Ss) ->
lists:any(fun (#c_bitstr{val=Val,size=Size}) ->
vu_expr(V, Val) orelse vu_expr(V, Size)
end, Ss).
%% Have to get the pattern results right.
-spec vu_clause(cerl:var_name(), cerl:c_clause()) -> boolean().
vu_clause(V, #c_clause{pats=Ps,guard=G,body=B}) ->
case vu_pattern_list(V, Ps) of
{true,_Shad} -> true; %It is used
{false,true} -> false; %Shadowed
{false,false} -> %Not affected
%% Neither used nor shadowed. Check guard and body.
vu_expr(V, G) orelse vu_expr(V, B)
end.
-spec vu_clauses(cerl:var_name(), [cerl:c_clause()]) -> boolean().
vu_clauses(V, Cs) ->
lists:any(fun(C) -> vu_clause(V, C) end, Cs).
%% vu_pattern(VarName, Pattern) -> {Used,Shadow}.
%% vu_pattern_list(VarName, [Pattern]) -> {Used,Shadow}.
%% Binaries complicate patterns as a variable can both be properly
%% used, in a bit segment size, and shadow. They can also do both.
%% vu_pattern(V, Pat) -> vu_pattern(V, Pat, {false,false}).
vu_pattern(V, #c_var{name=V2}, {Used,_}) ->
{Used,V =:= V2};
vu_pattern(V, #c_cons{hd=H,tl=T}, St0) ->
case vu_pattern(V, H, St0) of
{true,_}=St1 -> St1; %Nothing more to know
St1 -> vu_pattern(V, T, St1)
end;
vu_pattern(V, #c_tuple{es=Es}, St) ->
vu_pattern_list(V, Es, St);
vu_pattern(V, #c_binary{segments=Ss}, St) ->
vu_pat_seg_list(V, Ss, St);
vu_pattern(V, #c_map{es=Es}, St) ->
vu_map_pairs(V, Es, St);
vu_pattern(V, #c_alias{var=Var,pat=P}, St0) ->
case vu_pattern(V, Var, St0) of
{true,_}=St1 -> St1;
St1 -> vu_pattern(V, P, St1)
end;
vu_pattern(_, _, St) -> St.
vu_pattern_list(V, Ps) -> vu_pattern_list(V, Ps, {false,false}).
vu_pattern_list(V, Ps, St0) ->
lists:foldl(fun(P, St) -> vu_pattern(V, P, St) end, St0, Ps).
vu_pat_seg_list(V, Ss, St) ->
lists:foldl(fun(_, {true,_}=St0) -> St0;
(#c_bitstr{val=Val,size=Size}, St0) ->
case vu_pattern(V, Val, St0) of
{true,_}=St1 -> St1;
{false,Shad} ->
{vu_expr(V, Size),Shad}
end
end, St, Ss).
vu_map_pairs(V, [#c_map_pair{key=Key,val=Pat}|T], St0) ->
case vu_expr(V, Key) of
true ->
{true,false};
false ->
case vu_pattern(V, Pat, St0) of
{true,_}=St -> St;
St -> vu_map_pairs(V, T, St)
end
end;
vu_map_pairs(_, [], St) -> St.
-spec vu_var_list(cerl:var_name(), [cerl:c_var()]) -> boolean().
vu_var_list(V, Vs) ->
lists:any(fun (#c_var{name=V2}) -> V =:= V2 end, Vs).
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