Redefine TransformHelperButterfly::to_string to show butterfly opt flag.

 #275

src/faust_linear_operator/CPU/faust_TransformHelperButterfly.h

@@ -46,6 +46,7 @@ namespace Faust
 
 
 			public:
+			std::string to_string() const;
 			Vect<FPP, Cpu> multiply(const Vect<FPP, Cpu>& x);
 			void multiply(const FPP* x, FPP* y);
 			Vect<FPP,Cpu> multiply(const FPP* x);

src/faust_linear_operator/CPU/faust_TransformHelperButterfly.hpp

@@ -36,6 +36,15 @@ namespace Faust
 		}
 	}
 
+	template<typename FPP>
+		std::string TransformHelperButterfly<FPP,Cpu>::to_string() const
+		{
+			auto str = TransformHelper<FPP,Cpu>::to_string();
+			str += "- Butterfly structure optimized\r\n";
+			return str;
+		}
+
+
 	template<typename FPP>
 		TransformHelper<FPP,Cpu>* TransformHelperButterfly<FPP,Cpu>::fourierFaust(unsigned int n, const bool norma)
 		{