move to lib

cmd/divisors.go

@@ -20,71 +20,14 @@ import (
 	"fmt"
 
 	"github.com/spf13/cobra"
+	"scm.dairydemon.net/filifa/mathtools/internal/lib"
 )
 
 var divisorsN uint
 var divisorsE uint
 
-func pow(base uint, exp uint) uint {
-	result := uint(1)
-	for exp > 0 {
-		if exp%2 == 1 {
-			result *= base
-		}
-
-		exp >>= 1
-		base *= base
-	}
-
-	return result
-}
-
-func updateMultiples(sieve []uint, x uint, p uint, n uint) {
-	for q := p; ; q *= p {
-		// sigma_x(a*b) = sigma_x(a) * sigma_x(b) if gcd(a,b) = 1
-		for i := 2 * q; i < n; i += q {
-			if i%(p*q) != 0 {
-				sieve[i] *= sieve[q]
-			}
-		}
-
-		if p*q >= n {
-			break
-		}
-
-		// sigma_x(p^k) = p^(kx) + sigma_x(p^(k-1))
-		sieve[p*q] = pow(p*q, x) + sieve[q]
-	}
-}
-
-func divisorsSieve(n uint, x uint) chan uint {
-	sieve := make([]uint, n)
-	sieve[0] = 0
-	for i := uint(1); i < n; i++ {
-		sieve[i] = 1
-	}
-
-	ch := make(chan uint)
-	go func() {
-		for i := uint(0); i < n; i++ {
-			if i == 0 || i == 1 || sieve[i] != 1 {
-				ch <- sieve[i]
-				continue
-			}
-
-			sieve[i] = pow(i, x) + 1
-			updateMultiples(sieve, x, i, n)
-			ch <- sieve[i]
-		}
-
-		close(ch)
-	}()
-
-	return ch
-}
-
 func divisors(cmd *cobra.Command, args []string) {
-	ch := divisorsSieve(divisorsN, divisorsE)
+	ch := lib.DivisorsSieve(divisorsN, divisorsE)
 	for i := 0; ; i++ {
 		v, ok := <-ch
 		if !ok {