become a bit confused about FilledSamples and mixtures

fermi.go

@@ -21,6 +21,7 @@ type Stack struct {
 
 type Dist interface {
 	Samples() []float64
+	Sampler(sample.State) float64
 }
 
 type Scalar float64
@@ -48,21 +49,37 @@ func (p Scalar) Samples() []float64 {
 	}
 	return xs
 }
+func (p Scalar) Sampler(r sample.State) float64 {
+	return float64(p)
+}
 
 func (ln Lognormal) Samples() []float64 {
 	sampler := func(r sample.State) float64 { return sample.Sample_to(ln.low, ln.high, r) }
 	// Can't do parallel because then I'd have to await throughout the code
 	return sample.Sample_serially(sampler, N_SAMPLES)
 }
+func (ln Lognormal) Sampler(r sample.State) float64 {
+	return sample.Sample_to(ln.low, ln.high, r)
+}
 
 func (beta Beta) Samples() []float64 {
 	sampler := func(r sample.State) float64 { return sample.Sample_beta(beta.a, beta.b, r) }
 	return sample.Sample_serially(sampler, N_SAMPLES)
 }
+func (beta Beta) Sampler(r sample.State) float64 {
+	return sample.Sample_beta(beta.a, beta.b, r)
+}
 
 func (fs FilledSamples) Samples() []float64 {
 	return fs.xs
 }
+func (fs FilledSamples) Sampler(r sample.State) float64 {
+	// This is a bit subtle, because sampling from a FilledSamples item iteratively converges
+	// to something different than the initial distribution
+	n := len(fs.xs)
+	i := sample.Sample_int(n, r)
+	return fs.xs[i]
+}
 
 /* Constants */
 const HELP_MSG = "1. Grammar:\n" +

sample/sample.go

@@ -16,6 +16,10 @@ type func64 = func(State) float64
 
 var global_state = rand.New(rand.NewPCG(uint64(1), uint64(2)))
 
+func Sample_int(n int, r State) int {
+	return r.IntN(n)
+}
+
 func Sample_unit_uniform(r State) float64 {
 	return r.Float64()
 }