Decimal: implement IsInt

dec_test.go

@@ -49,20 +49,3 @@ func TestDec_digit(t *testing.T) {
 		})
 	}
 }
-
-var (
-	benchU uint
-)
-
-func BenchmarkDec_Digits(b *testing.B) {
-	rand.Seed(0xdeadbeefbadf00d)
-	d := dec(nil).make(10000)
-	for i := range d {
-		d[i] = Word(rand.Uint64()) % _BD
-	}
-	for i := 0; i < b.N; i++ {
-		d[0] = Word(rand.Uint64()) % _BD
-		d[len(d)-1] = Word(rand.Uint64()) % _BD
-		benchU = d.digits()
-	}
-}

decimal.go

@@ -79,7 +79,20 @@ func (x *Decimal) IsInf() bool {
 }
 
 func (x *Decimal) IsInt() bool {
-	panic("not implemented")
+	if debugDecimal {
+		x.validate()
+	}
+	// special cases
+	if x.form != finite {
+		return x.form == zero
+	}
+	// x.form == finite
+	if x.exp <= 0 {
+		return false
+	}
+	// x.exp > 0
+	// mant[0:prec] * 10**exp >= 0 || mant[0:mant.MinPrec()]*10**exp >= 0
+	return x.prec <= uint32(x.exp) || x.MinPrec() <= uint(x.exp)
 }
 
 func (x *Decimal) MantExp(mant *Decimal) (exp int) {

decimal_test.go

@@ -10,6 +10,8 @@ import (
 	"time"
 )
 
+var benchU uint
+
 var intData = []struct {
 	s  string
 	b  int