sine.go

package main

import (
    "math"
)

type Sine struct {
    freqPerSample float64
    phase float64
    multiplier float64
}

func NewSine(frequency, sampleRate, multiplier float64) *Sine {
    return &Sine{
        freqPerSample:  2 * math.Pi * frequency / sampleRate,
        multiplier: multiplier,
        phase: 0.0,
    }
}

func (s *Sine) Next() int64 {
    s.phase = s.phase + s.freqPerSample

    return int64(math.Sin(s.phase) * s.multiplier)
}