added simple fft

lib/simple_fft/fft_settings.h

@@ -0,0 +1,19 @@
+// In this file you can alter some settings of the library:
+// 1) Specify the desired real and complex types by typedef'ing real_type and complex_type.
+//    By default real_type is double and complex_type is std::complex<real_type>.
+// 2) If the array class uses square brackets for element access operator, define
+//    the macro __USE_SQUARE_BRACKETS_FOR_ELEMENT_ACCESS_OPERATOR
+
+#ifndef __SIMPLE_FFT__FFT_SETTINGS_H__
+#define __SIMPLE_FFT__FFT_SETTINGS_H__
+
+#include <complex>
+
+typedef double real_type;
+typedef std::complex<real_type> complex_type;
+
+//#ifndef __USE_SQUARE_BRACKETS_FOR_ELEMENT_ACCESS_OPERATOR
+//#define __USE_SQUARE_BRACKETS_FOR_ELEMENT_ACCESS_OPERATOR
+//#endif
+
+#endif // __SIMPLE_FFT__FFT_SETTINGS_H__