switch on type using new distribution interface

f.go

@@ -19,7 +19,20 @@ const GENERAL_ERR_MSG = "Valid inputs: 2 || * 2 || / 2 || 2 20 || * 2 20 || / 2
 
 type Dist interface {
 	Samples() []float64
-	Type() string
+}
+
+// Point implementing distribution
+
+type Scalar struct {
+	p float64
+}
+
+func (p Scalar) Samples() []float64 {
+	xs := make([]float64, 1_000_000)
+	for i := 0; i < 1_000_000; i++ {
+		xs[i] = p.p
+	}
+	return xs
 }
 
 // Lognormal implementing Distribution
@@ -62,21 +75,6 @@ func (beta FilledSamples) Type() string {
 	return "FilledSamples"
 }
 
-// Actually, I should look up how do do a) enums in go, b) union types
-/*type Lognormal struct {
-	low  float64
-	high float64
-}
-*/
-
-/*
-type Dist struct {
-	Type      string
-	Lognormal Lognormal
-	Samples   []float64
-}
-*/
-
 // Parse line into Distribution
 func parseLineErr(err_msg string) (string, Dist, error) {
 	fmt.Println(GENERAL_ERR_MSG)
@@ -157,10 +155,55 @@ func multiplyBetaDists(beta1 Beta, beta2 Beta) Beta {
 	return Beta{a: beta1.a + beta2.a, b: beta1.b + beta2.b}
 }
 
-func joinDists(old_dist Dist, new_dist Dist, op string) (Dist, error) {
-	switch {
+func multiplyAsSamples(dist1 Dist, dist2 Dist) Dist {
+	xs := dist1.Samples()
+	ys := dist2.Samples()
+	zs := make([]float64, 1_000_000)
+	for i, x := range xs {
+		zs[i] = x * ys[i]
 	}
 
+	return FilledSamples{xs: xs}
+}
+
+func multiplyDists(old_dist Dist, new_dist Dist) (Dist, error) {
+
+	switch o := old_dist.(type) {
+	case Lognormal:
+		{
+			switch n := new_dist.(type) {
+			case Lognormal:
+				return multiplyLogDists(o, n), nil
+			case Scalar:
+				return multiplyLogDists(o, Lognormal{low: n.p, high: n.p}), nil
+			default:
+				return multiplyAsSamples(o, n), nil
+			}
+		}
+	case Scalar:
+		{
+			switch n := new_dist.(type) {
+			case Lognormal:
+				return multiplyLogDists(Lognormal{low: o.p, high: o.p}, n), nil
+			case Scalar:
+				return Scalar{p: o.p * n.p}, nil
+			default:
+				return multiplyAsSamples(o, n), nil
+			}
+		}
+	default:
+		return nil, errors.New("Can't multiply dists")
+	}
+}
+
+func joinDists(old_dist Dist, new_dist Dist, op string) (Dist, error) {
+
+	switch op {
+	case "*":
+		return multiplyDists(old_dist, new_dist)
+	default:
+		return old_dist, errors.New("Can't combine distributions in this way")
+	}
 	/*
 		switch {
 		case old_dist.Type == "Lognormal" && new_dist.Type == "Lognormal" && op == "*":
@@ -172,7 +215,7 @@ func joinDists(old_dist Dist, new_dist Dist, op string) (Dist, error) {
 			fmt.Printf("For now, can't do anything besides multiplying lognormals\n")
 		}
 	*/
-	return old_dist, errors.New("Can't combine distributions in this way")
+	// return old_dist, errors.New("Can't combine distributions in this way")
 }
 
 /* Pretty print distributions */