So just to post again to make things clearer, right now algorithms tend to
look pretty ugly and obfuscated since you have to prefix function arguments
with the argument names using dot notation:
function tick (state::SvfSinOsc, coef::SvfSinOscCoef)
local v1::Float64 = coef.g0*state.ic1eq - coef.g1*state.ic2eq
local v2::Float64 = coef.g1*state.ic1eq + coef.g0*state.ic2eq
SvfSinOsc (2*v1 - state.ic1eq, 2*v2 - state.ic2eq)
end
This is a lot more readable to me, and it would be super useful to have a
"using" type operation similar to namespace but it could run on variables
instead, so that although writing the following is equivalent to what is
above, it is much easier to see what is going on:
function tick (state::SvfSinOsc, coef::SvfSinOscCoef)
using state, coef
local v1::Float64 = g0*ic1eq - g1*ic2eq
local v2::Float64 = g1*ic1eq + g0*ic2eq
SvfSinOsc (2*v1 - ic1eq, 2*v2 - ic2eq)
end
What are peoples opinions on this? Would anyone else find it useful?
On Friday, June 6, 2014 3:17:31 PM UTC+8, Andrew Simper wrote:
>
> In implementations where you want named data, I've noticed that the
> algorithm gets obfuscated by lots of variable names with dots after them.
> For example, here is a basic analog model of a state variable filter used
> as a sine wave generator:
>
> immutable SvfSinOscCoef
> g0::Float64
> g1::Float64
> end
> immutable SvfSinOsc
> ic1eq::Float64
> ic2eq::Float64
> end
> function SvfSinOscCoef_Init (;freq=1.0, sr=44100.0)
> local g::Float64 = tan (2pi*freq/sr)
> local g0 = 1.0/(1.0+g^2)
> SvfSinOscCoef (g0,g*g0)
> end
> function SvfSinOsc_Init (startphase::Float64)
> SvfSinOsc (cos(startphase), sin(startphase))
> end
>
> But the tick function looks a bit messy:
>
> function tick (state::SvfSinOsc, coef::SvfSinOscCoef)
> local v1::Float64 = coef.g0*state.ic1eq - coef.g1*state.ic2eq
> local v2::Float64 = coef.g1*state.ic1eq + coef.g0*state.ic2eq
> SvfSinOsc (2*v1 - state.ic1eq, 2*v2 - state.ic2eq)
> end
>
>
> It would be really cool if there was a way to shorthand the syntax of this
> to something like the following, which is a lot more readable:
>
> function tick (state::SvfSinOsc, coef::SvfSinOscCoef)
> using s, c
> local v1::Float64 = g0*ic1eq - g1*ic2eq
> local v2::Float64 = g1*ic1eq + g0*ic2eq
> SvfSinOsc (2*v1 - ic1eq, 2*v2 - ic2eq)
> end
>
>
> Lots of algorithms have arguments with the same type, but even then you
> could still specify using just the most used argument, but if it doesn't
> help make things more clear or isn't useful then people don't have to use
> it at all.
>
>
>
> Another pattern that would be nice to handle cleanly is: fetch state to
> local, compute on local, store local to state. I have written code that
> generates code to handle this since it is such a pain to keep everything in
> sync, but if there was some way to automate this at the language level then
> it would really rock, so here is an example of the longhand way, which
> isn't too bad for this example, but just imagine if there are 20 or so
> variables, and you are writing multiple tick functions:
>
> type SvfSinOsc
> ic1eq::Float64
> ic2eq::Float64
> end
>
> function tick (state::SvfSinOsc, coef::SvfSinOscCoef)
> local ic1eq::Float64 = state.ic1eq
> local ic2eq::Float64 = state.ic2eq
> for i = 1:100
> # compute algorithm using local copies of state.ic1eq and
> state.ic2eq
> end
> state.ic1eq = ic1eq
> state.ic2eq = ic2eq
> return state
> end
>
>
> I have a feeling that macros may be able to help out here to result in
> something like:
>
> function tick (state::SvfSinOsc, coef::SvfSinOscCoef)
> @fetch state
> for i = 1:100
> # compute iterative algorithm using local copies of state.ic1eq
> and state.ic2eq
> end
> @store state
> return state
> end
>
> But I'm not sure how to code such a beast, I tried something like:
>
> macro fetch(obj::SvfSinOsc)
> return quote
> local ic1eq = obj.ic1eq
> local ic2eq = obj.ic2eq
> end
> end
>
> macro store(obj::SvfSinOsc)
> return quote
> obj.ic1eq = ic1eq
> obj.ic2eq = ic2eq
> end
> end
>
> dump(osc)
> macroexpand (:(@fetch osc))
> macroexpand (:(@store osc))
>
> SvfSinOsc
> ic1eq: Float64 1.0
> ic2eq: Float64 0.0
>
>
> Out[28]: :($(Expr(:error,
> TypeError(:anonymous,"typeassert",SvfSinOsc,:osc))))
>
>
>
>
>
>
>
>
