Create sqrt.go

sqrt.go

@@ -0,0 +1,32 @@
+package decimal
+
+const SqrtMaxIter 100000
+
+// Sqrt returns the square root of d, the result will have
+// DivisionPrecision digits after the decimal point.
+func (d Decimal) Sqrt() Decimal {
+	s, _ := d.SqrtRound(int32(decimal.DivisionPrecision))
+	return s
+}
+
+// SqrtRound returns the square root of d, the result will have
+// precision digits after the decimal point. The bool precise returns whether the precision was reached
+func (d Decimal) SqrtRound(precision int32) (Decimal, bool) {
+	cutoff := New(1, -precision)
+	lo := Zero
+	hi := d
+	var mid Decimal
+	for i := 0; i < SqrtMaxIter; i++ {
+		//mid = (lo+hi)/2;
+		mid = lo.Add(hi).DivRound(New(2, 0), precision)
+		if mid.Mul(mid).Sub(d).Abs().LessThan(cutoff) {
+			return mid, true
+		}
+		if mid.Mul(mid).GreaterThan(d) {
+			hi = mid
+		} else {
+			lo = mid
+		}
+	}
+	return mid, false
+}