00:03 <lavaflow> ah, alright. I'll look into it further and also check out zealdocs

10:17 <jboy> I use this in vim instead of calling raco docs: autocmd FileType racket nmap <buffer> K :silent !zeal <cword><cr>:redraw!<cr>

20:01 <freeduck> Hi all. I would like to use array-fft in one of my projects. I am told my a friend that fft can identify the different frequencies that make up a signal. My math skill are limited, and I am looking for examples where fft is used. Can any of you point me the right direction? thanks

21:03 <rjungemann> @freeduck it's used frequently in music software for monophonic/polyphonic pitch detection, pitch/formant shifting, and vocoders, and also frequently used in the sciences

21:05 <rjungemann> It takes a signal (in the frequency domain) and breaks it up into "buckets" where each bucket represents a sine wave of a certain frequency, with a certain amplitude

21:06 <rjungemann> You can use it for analysis, or you can manipulate the amplitudes of the buckets and use an inverse FFT to generate a new signal

21:07 <rjungemann> My favorite use is "spectral freezing"—track a handful of snapshots of the FT and then cycle through them and IFFT to create an apparent "frozen" version of a sound, like a sustain pedal for any sound

21:08 <rjungemann> For more info you can look up "spectral sound processing". It really sank in for me what an FFT does when I learned about additive synthesis, which is a little bit like an IFFT

21:09 <rjungemann> To use for monophonic pitch detection, a good place to start is to loop through the buckets and find the one with the highest amplitude

21:28 <rjungemann> If I'm inside of a macro, and I have a syntax-wrapped hash, let's say, how can I use it? Calling `(hash-has-key? #'my-hash #'my-key)` returns `hash-has-key?: contract violation expected: hash? given: #<syntax #hash()>`

21:30 <rjungemann> Ah, `syntax-e` does it. It makes me nervous because I've read the docs on it a dozen times and I still don't "get" `syntax-e` but at least it seems to work

21:31 <rjungemann> I've been writing unhygenic macros for a long time, and so I tend to start with `define-macro`and then port it to hygenic, but there's so much to learn...

21:34 <rjungemann> Here's another question. If I have a macro that only modifies a syntax parameter and doesn't need to generate a body necessarily, is there a way to define a function at the syntax level and make it available for calling outside of a macro? If I define a function in `begin-for-syntax` it isn't available outside

22:13 <rjungemann> I don't know if this is interesting to anyone, but I wrote my own take on multiple dispatch based on Clojure's `defmulti`. It boils down to an inline `cond` so it should be stupid fast. I'll be using it as a library for my Lisp game jam game, to dispatch an `update` method based on an entity's name (there are reasons for not using alternatives which are too complicated to unpack atm)

22:13 <rjungemann> https://gist.github.com/db149400ca095d97fa953345409ac7f6

22:14 <rjungemann> If anyone would like to poke holes in my insane attempt at converting my unhygenic macros to hygenic, please do, I'd like to get better (the commented-out code is the unhygenic original version)

22:15 <rjungemann> I feel like I'm using `syntax-e` and `syntax->datum` way way too much...

22:15 <rjungemann> Oh and the example code is in the `main` module at the bottom