compute convergents with channels

cmd/convergents.go

@@ -23,45 +23,49 @@ import (
 	"github.com/spf13/cobra"
 )
 
-func gaussianBrackets(x, xprev, a *big.Int) {
-	tmp := new(big.Int)
-	tmp.Mul(a, x)
-	tmp.Add(tmp, xprev)
-	xprev.Set(x)
-	x.Set(tmp)
+func cycle(seq []*big.Int, ch chan *big.Int) {
+	n := len(seq)
+	for i := 0; true; i = (i + 1) % n {
+		ch <- seq[i]
+	}
+}
+
+func gaussianBrackets(x, xprev *big.Int, seq []*big.Int, ch chan *big.Int) {
+	c := make(chan *big.Int)
+	go cycle(seq, c)
+	for a := range c {
+		tmp := new(big.Int)
+		tmp.Mul(a, x)
+		tmp.Add(tmp, xprev)
+		xprev.Set(x)
+		x.Set(tmp)
+		ch <- tmp
+	}
 }
 
 func convergents(cmd *cobra.Command, args []string) {
-	hprev := big.NewInt(0)
-	kprev := big.NewInt(1)
-
-	h := big.NewInt(1)
-	k := big.NewInt(0)
-
 	a0, ok := new(big.Int).SetString(args[0], 10)
 	if !ok {
 		cobra.CheckErr("invalid input " + args[0])
 	}
 
-	denoms := make([]big.Int, len(args[1:]))
+	denoms := make([]*big.Int, len(args[1:]))
 	for i, d := range args[1:] {
-		_, ok = denoms[i].SetString(d, 10)
+		denoms[i] = new(big.Int)
+		_, ok := denoms[i].SetString(d, 10)
 		if !ok {
 			cobra.CheckErr("invalid input " + d)
 		}
 	}
 
-	gaussianBrackets(h, hprev, a0)
-	gaussianBrackets(k, kprev, a0)
-
-	r := new(big.Rat).SetFrac(h, k)
-	fmt.Println(r)
-
-	for i := 0; true; i = (i + 1) % len(denoms) {
-		a := &denoms[i]
-		gaussianBrackets(h, hprev, a)
-		gaussianBrackets(k, kprev, a)
+	hch := make(chan *big.Int)
+	kch := make(chan *big.Int)
+	go gaussianBrackets(a0, big.NewInt(1), denoms, hch)
+	go gaussianBrackets(big.NewInt(1), big.NewInt(0), denoms, kch)
 
+	r := new(big.Rat)
+	for {
+		h, k := <-hch, <-kch
 		r.SetFrac(h, k)
 		fmt.Println(r)
 	}