The approach I'd use might be a little different. Vivid offers a "toI" function which takes any number and converts it to an "I".

So for example:

myNums = [1..10] :: [Double]

sd0 = undefined :: SynthDef '["freq"]
sd1 = undefined :: SynthDef '["amp"]

main = do
   s0 <- synth sd0
   s1 <- synth sd1
   forM_ myNums $ \n -> do
      set s0 (toI n :: I "freq")
      set s1 (toI n :: I "amp")

Also: "toI" works on any numeric type (any "Real n"), and "I" itself is a numeric type. So you can always write:

x = 5 :: I "freq"
y = toI x :: I "amp"


El 4 jul 2018, a las 08:30, Jeffrey Brown <> escribió:

Composers reuse melodic material across different instruments. I would like to do that in Vivid. I would keep a sequence of values and send it sometimes to one parameter of one synth, sometimes to a different parameter of a different synth.

To do that I would have to coerce those numbers to values of type `I a`, where the string `a` is known only at runtime. I tried to write a function to do that:

    import GHC.TypeLits
    toIOf :: (Real n, GHC.TypeLits.KnownSymbol a) => String -> n -> I a
    toIOf "freq" n = toI n :: I "freq"
    toIOf "amp" n = toI n :: I "amp"

but it won't compile, because the outputs of `toIOf "freq"` and `toIOf "amp"` have different types.

Is this possible?

Jeff Brown | Jeffrey Benjamin Brown
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