chore: add grug-math

grug/math/math.go

@@ -0,0 +1,189 @@
+// grug math is an unbounded precision math library for integers. It is not designed to be performant in any means. But as an example of how one works.
+package math
+
+import "strconv"
+
+type Number []rune
+
+func NewNumber() *Number {
+	return &Number{}
+}
+
+func (*Number) FromString(s string) *Number {
+	for _, a := range s {
+		if !(a >= '0' && a <= '9') {
+			return nil
+		}
+	}
+
+	var n Number = []rune(s)
+	
+	i:=0
+	for range n[:len(n)-1] {
+		if n[i] == 0 || n[i] == '0' {
+			i++
+		} else {
+			break
+		}
+	}
+	n = n[i:]
+
+	return &n
+}
+
+func (*Number) FromInt(i int) *Number {
+	s := strconv.Itoa(i)
+	var n Number = []rune(s)
+	return &n
+}
+
+func (n *Number) String() string {
+	if n == nil || len(*n) == 0 {
+		return "NaN"
+	}
+	return string(*n)
+}
+
+func (n *Number) Add(a *Number) *Number {
+	if n == nil || a == nil {
+		return nil
+	}
+
+	lenN, lenA := len(*n), len(*a)
+	sum := make(Number, max(lenN, lenA)+1)
+
+	for i := range sum[:len(sum)-1] {
+		ii := len(sum) - i - 1
+
+		switch {
+		case lenN == lenA:
+			j := (*n)[lenN-i-1]
+			k := (*a)[lenA-i-1]
+
+			sum[ii-1], sum[ii] = add(j, k, sum[ii])
+
+		case lenN > lenA:
+			j := (*n)[lenN-i-1]
+			k := '0'
+			if i < lenA {
+				k = (*a)[lenA-i-1]
+			}
+
+			sum[ii-1], sum[ii] = add(j, k, sum[ii])
+
+		case lenN < lenA:
+			j := '0'
+			if i < lenN {
+				j = (*n)[lenN-i-1]
+			}
+			k := (*a)[lenA-i-1]
+
+			sum[ii-1], sum[ii] = add(j, k, sum[ii])
+		}
+	}
+
+	// Trim the extra 0 if present
+	if sum[0] == 0 || sum[0] == '0' {
+		sum = sum[1:]
+	}
+
+	return &sum
+}
+
+
+func (n *Number) Sub(s *Number) *Number {
+	if n == nil || s == nil {
+		return nil
+	}
+
+	lenN, lenA := len(*n), len(*s)
+	sum := make(Number, max(lenN, lenA)+1)
+
+	for i := range sum[:len(sum)-1] {
+		ii := len(sum) - i - 1
+
+		switch {
+		case lenN == lenA:
+			j := (*n)[lenN-i-1]
+			k := (*s)[lenA-i-1]
+			c := '0'
+			if i+1 < lenN {
+				c = (*n)[lenN-i-2]
+			}
+
+			sum[ii-1], sum[ii] = sub(j, k, c)
+
+		case lenN > lenA:
+			j := (*n)[lenN-i-1]
+			k := '0'
+			if i < lenA {
+				k = (*s)[lenA-i-1]
+			}
+			c := '0'
+			if i+1 < lenN {
+				c = (*n)[lenN-i-2]
+			}
+
+			sum[ii-1], sum[ii] = sub(j, k, c)
+			if i+1 < lenN {
+				(*n)[lenN-i-2] =sum[ii-1]
+			}
+
+		case lenN < lenA:
+			j := '0'
+			if i < lenN {
+				j = (*n)[lenN-i-1]
+			}
+			k := (*s)[lenA-i-1]
+			c := '0'
+			if i+1 < lenN {
+				c = (*n)[lenN-i-2]
+			}
+
+			sum[ii-1], sum[ii] = sub(j, k, c)
+		}
+	}
+
+	// Trim the extra 0 if present
+	i:=0
+	for range sum[:len(sum)-1] {
+		if sum[i] == 0 || sum[i] == '0' {
+			i++
+		} else {
+			break
+		}
+	}
+	sum = sum[i:]
+
+
+	return &sum
+}
+
+
+func friends(r rune) (int32, int32) {
+	return 1, 10 - int32(r-'0')
+}
+func add(a, b, c rune) (rune, rune) {
+	up, dn := friends(b)
+	if c == 0 {
+		c = '0'
+	}
+	a = a + c - '0'
+
+	if a-dn < '0' {
+		return '0', a + b - '0'
+	}
+	return c + up, a - dn
+}
+
+func sub(a, b, c rune) (rune, rune) {
+	dn, up := friends(b)
+	if c == 0 {
+		c = '0'
+	}
+
+	if a+up > '9' {
+		return c, a - b + '0'
+	}
+	return c - dn, a + up
+}

grug/math/math_test.go

@@ -0,0 +1,74 @@
+package math_test
+
+import (
+	"testing"
+
+	"github.com/matryer/is"
+	"go.sour.is/pkg/grug/math"
+)
+
+func TestNumber(t *testing.T) {
+	is := is.New(t)
+
+	n := math.NewNumber().FromInt(100)
+	is.Equal(n.String(), "100")
+
+	n = n.FromString("00001")
+	is.Equal(n.String(), "1")
+
+	n = n.FromString("1x0")
+	is.True(n==nil)
+	is.Equal(n.String(), "NaN")
+
+	n = n.FromString("200")
+	is.True(n!=nil)
+	is.Equal(n.String(), "200")
+
+	n = (&math.Number{}).FromString("300")
+	is.True(n!=nil)
+	is.Equal(n.String(), "300")
+}
+
+func TestAdd(t *testing.T) {
+	is := is.New(t)
+
+	n := math.NewNumber().FromString("100")
+
+	n = n.Add(nil)
+	is.Equal(n.String(), "NaN")
+
+	n = n.FromInt(100)
+	n = n.Add(n.FromString("900"))
+	is.Equal(n.String(), "1000")
+
+	n = n.Add(math.NewNumber())
+	is.Equal(n.String(), "1000")
+
+	n = n.Add(n.FromString("10"))
+	is.Equal(n.String(), "1010")
+
+	n = n.Add(n.FromString("10000"))
+	is.Equal(n.String(), "11010")
+
+	n = n.Add(n.FromString("9000"))
+	is.Equal(n.String(), "20010")
+}
+
+func TestSub(t *testing.T) {
+	is := is.New(t)
+
+	n := math.NewNumber()
+
+	// n = n.FromString("100")
+	// n = n.Sub(n.FromInt(100))
+	// is.Equal(n.String(), "0")
+
+	// n = n.FromString("200")
+	// n = n.Sub(n.FromInt(100))
+	// is.Equal(n.String(), "100")
+
+	n = n.FromString("100")
+	n = n.Sub(n.FromInt(50))
+	is.Equal(n.String(), "50")
+
+}