kmx.io/pure/src/pure.erl

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• Hash : b680684f
  Author : Thomas de Grivel
  Date : 2022-02-17T11:36:40
  

  Purely functional Elixir
  

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• src/pure.erl

• -module(pure).
  
  -export([is_pattern_expr/1]).
  
  -import(lists, [all/2]).
  
  is_pattern_expr(Expr) ->
      case is_pattern_expr_1(Expr) of
  	false -> false;
  	true ->
  	    %% Expression is syntactically correct - make sure that it
  	    %% also can be evaluated.
  	    case erl_eval:partial_eval(Expr) of
  		{integer,_,_} -> true;
  		{char,_,_} -> true;
  		{float,_,_} -> true;
  		{atom,_,_} -> true;
  		{var,_,_} -> true;
                  {tuple,_,_} -> true;
  		X -> io:write(X), false
  	    end
      end.
  
  is_pattern_expr_1({char,_Anno,_C}) -> true;
  is_pattern_expr_1({integer,_Anno,_I}) -> true;
  is_pattern_expr_1({float,_Anno,_F}) -> true;
  is_pattern_expr_1({atom,_Anno,_A}) -> true;
  is_pattern_expr_1({tuple,_Anno,Es}) ->
      all(fun is_pattern_expr/1, Es);
  is_pattern_expr_1({var,_Anno,_V}) -> true;
  is_pattern_expr_1({nil,_Anno}) -> true;
  is_pattern_expr_1({cons,_Anno,H,T}) ->
      is_pattern_expr_1(H) andalso is_pattern_expr_1(T);
  is_pattern_expr_1({op,_Anno,Op,A}) ->
      erl_internal:arith_op(Op, 1) andalso is_pattern_expr_1(A);
  is_pattern_expr_1({op,_Anno,Op,A1,A2}) ->
      erl_internal:arith_op(Op, 2) andalso all(fun is_pattern_expr/1, [A1,A2]);
  is_pattern_expr_1(_Other) -> false.
  

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