melrōse musical expression player

package op import ( "fmt" "math/rand" "time" "github.com/emicklei/melrose/core" ) /** prob(0.8,note('c')) = a sequence with 80% chance of playing C **/ type Probability struct { chance core.HasValue seed *rand.Rand target core.HasValue } func NewProbability(chance, target core.HasValue) *Probability { return &Probability{ chance: chance, seed: rand.New(rand.NewSource(time.Now().Unix())), target: target, } } func (p *Probability) ToNote() (core.Note, error) { v := p.target.Value() nc, ok := v.(core.NoteConvertable) if !ok { return core.Rest4, fmt.Errorf("expect a Note but got %T", v) } note, err := nc.ToNote() if err != nil { return core.Rest4, err } if p.hit() { return note, nil } return note.ToRest(), nil } func (p *Probability) S() core.Sequence { seq := core.ToSequenceable(p.target).S() if p.hit() { return seq } return seq.ToRest() } func (p *Probability) hit() bool { f := core.Float(p.chance) if f > 1 { f = f / 100.0 } a := p.seed.Float32() return a <= f }