lmul! should be required for in-place application of plans

[dlfivefifty]

Overall, I like the overriding of * for planned transforms. But it is a bit odd that * modifies what you multiply in the following:

P = plan_fft!(x); P * x 

I would propose deprecating plan_fft!, and instead only have plan_fft with the following usage for the in-place variants:

P = plan_fft(x); lmul!(P, x)

[stevengj]

This won’t work, because the plan has to know it is in-place when it is created. In-place FFT algorithms are different from out-of-place algorithms.

[dlfivefifty]

Ah ok. So then I guess the proposal would be:

P = plan_fft!(x)
P * x # equivalent to the current P * copy(x)
lmul!(P, x) # equivalent to the current P * x

[stevengj]

Yes, that sounds reasonable.