Chris@25: !function() {
Chris@25: 
Chris@25:   var EPSILON = 1e-4,
Chris@25:       assert = require('assert'),
Chris@25:       complex_array_lib = require('../lib/complex_array'),
Chris@25:       fft_lib = require('../lib/fft'),
Chris@25:       ComplexArray = complex_array_lib.ComplexArray,
Chris@25:       isComplexArray = complex_array_lib.isComplexArray,
Chris@25:       PI = Math.PI,
Chris@25:       SQRT2 = Math.SQRT2,
Chris@25:       SQRT1_2 = Math.SQRT1_2,
Chris@25:       cos = Math.cos,
Chris@25:       sin = Math.sin,
Chris@25:       sqrt = Math.sqrt
Chris@25: 
Chris@25:   global.assertComplexArraysAlmostEqual = function(first, second) {
Chris@25:     var message = second + ' != ' + first
Chris@25: 
Chris@25:     assert.equal(first.length, second.length, message)
Chris@25: 
Chris@25:     first.forEach(function(value, i) {
Chris@25:       assertApproximatelyEqual(value.real, second.real[i], message)
Chris@25:       assertApproximatelyEqual(value.imag, second.imag[i], message)
Chris@25:     })
Chris@25:   }
Chris@25: 
Chris@25:   global.assertFFTMatches = function(original, expected) {
Chris@25:     var transformed, copy
Chris@25: 
Chris@25:     if (!isComplexArray(expected)) {
Chris@25:       throw TypeError('expected match should be a ComplexArray')
Chris@25:     }
Chris@25: 
Chris@25:     copy = new ComplexArray(original)
Chris@25:     transformed = fft_lib.FFT(original)
Chris@25:     assertComplexArraysAlmostEqual(expected, transformed)
Chris@25:     assertComplexArraysAlmostEqual(copy, fft_lib.InvFFT(transformed))
Chris@25:   }
Chris@25: 
Chris@25:    global.assertFFTMatchesDFT = function(input) {
Chris@25:     input = new ComplexArray(input)
Chris@25: 
Chris@25:     assertComplexArraysAlmostEqual(DFT(input), fft_lib.FFT(input))
Chris@25:   }
Chris@25: 
Chris@25:   global.DFT = function(input) {
Chris@25:     var n = input.length,
Chris@25:         amplitude = 1 / sqrt(n),
Chris@25:         output = new ComplexArray(input),
Chris@25:         phase = {real: 0, imag: 0},
Chris@25:         delta = {real: 0, imag: 0},
Chris@25:         i, j,
Chris@25:         _swap
Chris@25: 
Chris@25:     if (!isComplexArray(input)) {
Chris@25:       input = new ComplexArray(input)
Chris@25:     }
Chris@25: 
Chris@25:     for(i = 0; i < n; i++) {
Chris@25:       output.real[i] = 0, output.imag[i] = 0
Chris@25:       phase.real = 1, phase.imag = 0
Chris@25:       delta.real = cos(2*PI*i/n), delta.imag = sin(2*PI*i/n)
Chris@25: 
Chris@25:       for(j = 0; j < n; j++) {
Chris@25:         output.real[i] += phase.real * input.real[j] - phase.imag * input.imag[j]
Chris@25:         output.imag[i] += phase.real * input.imag[j] + phase.imag * input.real[j]
Chris@25:         _swap = phase.real
Chris@25:         phase.real = phase.real * delta.real - phase.imag * delta.imag
Chris@25:         phase.imag = _swap * delta.imag + phase.imag * delta.real
Chris@25:       }
Chris@25:       output.real[i] *= amplitude
Chris@25:       output.imag[i] *= amplitude
Chris@25:     }
Chris@25: 
Chris@25:     return output
Chris@25:   }
Chris@25: 
Chris@25:   function assertApproximatelyEqual(first, second, message) {
Chris@25:     var delta = Math.abs(first - second)
Chris@25:     assert.ok(delta < EPSILON, message)
Chris@25:   }
Chris@25: 
Chris@25: }()