Scott Michel
I might be missing something in translation, but if I understand Takayuki's message's intent, everything needs to be calculated because the C-based FFTW library is called (eventually). Laziness doesn't really have an impact.
The choice of underlying data structure and whether FFTW wisdom is used clearly has a significant impact.
If the Haskell wrapper library is a thick enough, lazy layer around
FFTW, the size of the result vector may not at all depend on any FFTW
computation.
Again, I have no experience at all with FFTW or any Haskell bindings to
it. This is just a general remark that is worth keeping in mind.
Greets,
Ertugrul
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Key-ID: E5DD8D11 "Ertugrul Soeylemez