decision simple no hay arreglos, Prolog

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objeto :- write('{'), atributo, write('}'). 
atributo :- read(C),write('"'),write(C),write('"'), 
            write(':'), M=True,valor(C,M), a1.
a1 :- read(X),(X='atributo'-> write(','),atributo;
               X='fin'->write('');
               write('error '), write(X)).
cadena :- read(C),write('"'),write(C),write('"').
valor(C,M) :- read(T),(T='cadena'->cadena;
                  T='numero'-> read(N),write(N);
                  T='objeto'->objeto;
                  M=True->(T='metodo'->metodo(C));
                  write('error'),write(T)).
metodo(C) :- write('"function() {'), 
             instruccion,
             write('return '), write(C),write(';}"'). 
instruccion :- read(I),
              (I='asignacion'->asignacion, instruccion;
               I='decision'->decision, instruccion;
               I='fin'->write('')).  
asignacion :- read(Var), write(Var), write('='),
              read(Exp), write(Exp), write('; ').
decision :- write('if ('),read(Condicion),write(Condicion),write(') '),
            write('{'),instruccion,write('} ').              
              
:- objeto.

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