Fast Fourier transform: Difference between revisions
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m (→{{header|REXX}}: changed whitespace and indentations, optimized a computation.) |
(→{{header|Perl 6}}: give terser functional version, along with its drawback and fix) |
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<lang perl6>sub fft { |
<lang perl6>sub fft { |
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@_ == 1 ?? @_ !! |
@_ == 1 ?? @_ !! |
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fft(@_[0,2...*]) «+« |
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fft(@_[1,3...*]) «*« map &cis, (0,-τ/@_...^-τ) |
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}</lang> |
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This particular version is numerically inaccurate though, because of the pi approximation. It is possible to fix it with the 'cisPi' function available in the TrigPi module: |
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<lang perl6>sub fft { |
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use TrigPi; |
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@_ == 1 ?? @_ !! |
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fft(@_[0,2...*]) «+« |
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fft(@_[1,3...*]) «*« map &cisPi, (0,-2/@_...^-2) |
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}</lang> |
}</lang> |
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