{-# OPTIONS -O2 -fno-implicit-prelude -fglasgow-exts #-} {- | Copyright : (c) Henning Thielemann 2006 License : GPL Maintainer : synthesizer@henning-thielemann.de Stability : provisional Portability : requires multi-parameter type classes Waveforms which are smoothed according to the oscillator frequency in order to suppress aliasing effects. -} module Synthesizer.Basic.WaveSmoothed ( T, fromFunction, fromWave, fromControlledWave, raise, amplify, distort, apply, sine, cosine, saw, square, triangle, Wave.Harmonic, Wave.harmonic, composedHarmonics, ) where import qualified Synthesizer.Basic.Wave as Wave import qualified Synthesizer.Basic.Phase as Phase -- import qualified Algebra.RealTranscendental as RealTrans import qualified Algebra.Transcendental as Trans -- import qualified Algebra.RealField as RealField import qualified Algebra.Module as Module import qualified Algebra.Field as Field import qualified Algebra.Real as Real import qualified Algebra.Ring as Ring import qualified Algebra.Additive as Additive import qualified MathObj.Polynomial as Poly import qualified Number.Complex as Complex import NumericPrelude -- import qualified Prelude as P import PreludeBase {- * Definition and construction -} newtype T t y = Cons {decons :: t -> Phase.T t -> y} {-# INLINE fromFunction #-} fromFunction :: (t -> t -> y) -> (T t y) fromFunction wave = Cons (\f p -> wave f (Phase.toRepresentative p)) {- | Use this function for waves which are sufficiently smooth. If the Nyquist frequency is exceeded the wave is simply replaced by a constant zero wave. -} {-# INLINE fromWave #-} fromWave :: (Field.C t, Real.C t, Additive.C y) => Wave.T t y -> (T t y) fromWave wave = fromControlledWaveAux (\f -> if abs f >= 1/2 then zero else wave) {-# INLINE fromControlledWave #-} fromControlledWave :: (Field.C t, Real.C t, Additive.C y) => (t -> Wave.T t y) -> (T t y) fromControlledWave wave = fromControlledWaveAux (\f0 -> let f = abs f0 in if f >= 1/2 then zero else wave f) {-# INLINE fromControlledWaveAux #-} fromControlledWaveAux :: (t -> Wave.T t y) -> (T t y) fromControlledWaveAux wave = Cons (\f p -> Wave.apply (wave f) p) {- * Operations on waves -} {-# INLINE raise #-} raise :: (Additive.C y) => y -> T t y -> T t y raise y = distort (y+) {-# INLINE amplify #-} amplify :: (Ring.C y) => y -> T t y -> T t y amplify k = distort (k*) {-# INLINE distort #-} distort :: (y -> z) -> T t y -> T t z distort g (Cons w) = Cons (\f p -> g (w f p)) {-# INLINE apply #-} apply :: T t y -> (t -> Phase.T t -> y) apply = decons instance Additive.C y => Additive.C (T t y) where {-# INLINE zero #-} {-# INLINE (+) #-} {-# INLINE (-) #-} {-# INLINE negate #-} zero = Cons (const zero) (+) (Cons w) (Cons v) = Cons (\f p -> w f p + v f p) (-) (Cons w) (Cons v) = Cons (\f p -> w f p - v f p) negate = distort negate instance Module.C a y => Module.C a (T t y) where {-# INLINE (*>) #-} s *> w = distort (s*>) w {- * Examples -} {- ** unparameterized -} {- | map a phase to value of a sine wave -} {-# INLINE sine #-} sine :: (Trans.C a, Real.C a) => T a a sine = fromWave Wave.sine {-# INLINE cosine #-} cosine :: (Trans.C a, Real.C a) => T a a cosine = fromWave Wave.cosine {- | saw tooth, it's a ramp down in order to have a positive coefficient for the first partial sine -} {-# INLINE saw #-} saw :: (Real.C a, Field.C a) => T a a saw = fromControlledWave (\f -> Wave.triangleAsymmetric (2*f-1)) {- | square -} {-# INLINE square #-} square :: (Real.C a, Field.C a) => T a a square = fromControlledWave (\f -> Wave.trapezoid (1-2*f)) {- | triangle -} {-# INLINE triangle #-} triangle :: (Real.C a, Field.C a) => T a a triangle = fromWave Wave.triangle {- | Specify the wave by its harmonics. The function is implemented quite efficiently by applying the Horner scheme to a polynomial with complex coefficients (the harmonic parameters) using a complex exponential as argument. -} {-# INLINE composedHarmonics #-} composedHarmonics :: (Trans.C a, Real.C a) => [Wave.Harmonic a] -> T a a composedHarmonics hs = let c = map (\h -> Complex.fromPolar (Wave.harmonicAmplitude h) (2*pi * Phase.toRepresentative (Wave.harmonicPhase h))) hs -- @take (ceiling (1/(2*f)))@ would fail for small @f@ especially @f==zero@ trunc f = map snd . takeWhile ((<1/2) . fst) . zip (iterate (abs f +) zero) in fromControlledWaveAux $ \f -> Wave.distort (Complex.imag . Poly.evaluate (Poly.fromCoeffs (trunc f c))) Wave.helix {- GNUPlot.plotFunc [] (GNUPlot.linearScale 1000 (0,1::Double)) (composedHarmonics [harmonic 0 0, harmonic 0 0, harmonic 0 0, harmonic 0.25 1]) -}