Update README.md

Author: mahmudsudo

README.md

@@ -1 +1,22 @@
 # fft_rs
+Fast Fourier Transform implementation in Rust.
+
+https://en.wikipedia.org/wiki/Fast_Fourier_transform & DFT
+
+Usage
+let values: Vec<f64> = vec![0.2, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8];
+
+// compute the FFT (Fast Fourier Transform)
+let fft_res = fft(&values);
+
+// compute the IFFT (Inverse Fast Fourier Transform)
+let ifft_res = ifft(&fft_res);
+
+
+// Also, available directly (and slower) DFT & IDFT:
+
+// compute the DFT (Discrete Fourier Transform)
+let dft_res = dft(&values);
+
+// compute the IDFT (Inverse Discrete Fourier Transform)
+let idft_res = idft(&dft_res)