Data update

Task/Fast-Fourier-transform/EasyLang/fast-fourier-transform.easy

@@ -0,0 +1,44 @@
+sysconf radians
+func[] cmult a[] b[] .
+   return [ a[1] * b[1] - a[2] * b[2] a[1] * b[2] + a[2] * b[1] ]
+.
+func[] cadd a[] b[] .
+   return [ a[1] + b[1] a[2] + b[2] ]
+.
+func[] csub a[] b[] .
+   return [ a[1] - b[1] a[2] - b[2] ]
+.
+func[] cexp a[] .
+   p = pow 2.718281828459045235 a[1]
+   return [ p * cos a[2] p * sin a[2] ]
+.
+func cabs a[] .
+   return sqrt (a[1] * a[1] + a[2] * a[2])
+.
+proc fft x[] . y[][] .
+   n = len x[]
+   if n = 1
+      y[][] = [ [ x[1] 0 ] ]
+      return
+   .
+   for i = 1 step 2 to len x[]
+      xeven[] &= x[i]
+      xodd[] &= x[i + 1]
+   .
+   fft xeven[] even[][]
+   fft xodd[] odd[][]
+   y[][] = [ ]
+   for k to n div 2
+      t[][] &= cmult cexp [ 0 -2 * pi * (k - 1) / n ] odd[k][]
+   .
+   for k to n div 2
+      y[][] &= cadd even[k][] t[k][]
+   .
+   for k to n div 2
+      y[][] &= csub even[k][] t[k][]
+   .
+.
+fft [ 1.0 1.0 1.0 1.0 0.0 0.0 0.0 0.0 ] r[][]
+for i to len r[][]
+   write cabs r[i][] & " "
+.