dec: remove fnorm() call in dec.setInt

This is to keep the dec implementation in line with big.nat: all
dec member functions assume right-aligned numbers.

dec.go

@@ -93,9 +93,8 @@ func (z dec) setWord(x Word) dec {
 	return z
 }
 
-// setInt sets z such that z*10**exp = x with 0 < z <= 1.
-// Returns z and exp.
-func (z dec) setInt(x *big.Int) (dec, uint) {
+// setInt sets z = x.mant
+func (z dec) setInt(x *big.Int) dec {
 	bb := x.Bits()
 	// TODO(db47h): here we cannot directly copy(b, bb)
 	b := make([]Word, len(bb))
@@ -107,11 +106,7 @@ func (z dec) setInt(x *big.Int) (dec, uint) {
 		z[i] = Word(divWVW(b, 0, b, _BD))
 	}
 	z = z.norm()
-	if len(z) == 0 {
-		return z, 0
-	}
-	s := dnorm(z)
-	return z, uint(len(z))*_WD - uint(s)
+	return z
 }
 
 // sticky returns 1 if there's a non zero digit within the

dec_test.go

@@ -1,7 +1,6 @@
 package decimal
 
 import (
-	"math/big"
 	"math/bits"
 	"math/rand"
 	"reflect"
@@ -46,11 +45,11 @@ func Test_mag(t *testing.T) {
 
 // TODO(db47h): remove this function
 func Test_dec_setInt(t *testing.T) {
-	// TODO(db47h): next step
-	b, _ := new(big.Int).SetString("12345678901234567890", 0)
-	d, exp := dec{}.make(3).setInt(b)
-	t.Log(d, exp)
-	t.Log(string(dtoa(d, 10)))
+	// // TODO(db47h): next step
+	// b, _ := new(big.Int).SetString("12345678901234567890", 0)
+	// d, exp := dec{}.make(3).setInt(b)
+	// t.Log(d, exp)
+	// t.Log(string(dtoa(d, 10)))
 }
 
 func Test_add10VW(t *testing.T) {

decimal.go

@@ -194,9 +194,9 @@ func (z *Decimal) SetInt(x *big.Int) *Decimal {
 		return z
 	}
 	// x != 0
-	exp := uint(0)
-	z.mant, exp = z.mant.make((int(prec) + _WD - 1) / _WD).setInt(x)
-	z.setExpAndRound(int64(exp), 0)
+	z.mant = z.mant.make((int(prec) + _WD - 1) / _WD).setInt(x)
+	exp := dnorm(z.mant)
+	z.setExpAndRound(int64(len(z.mant))*_WD-exp, 0)
 	return z
 }
 

decimal_test.go

@@ -12,19 +12,21 @@ import (
 
 var intData = []struct {
 	s  string
+	b  int
 	p  uint
 	d  dec
 	pr uint
 	e  int32
 }{
-	{"1234567890123456789_0123456789012345678_9012345678901234567_8901234567890123456_78901234567890", 0,
+	{"00000000000000000001232", 10, 0, dec{1232000000000000000}, 19, 4},
+	{"1234567890123456789_0123456789012345678_9012345678901234567_8901234567890123456_78901234567890", 0, 0,
 		dec{7890123456789000000, 8901234567890123456, 9012345678901234567, 123456789012345678, 1234567890123456789},
 		90, 90},
-	{"1235", 0, dec{1235000000000000000}, _WD, 4},
-	{"1235", 3, dec{1240000000000000000}, 3, 4},
-	{"1245", 3, dec{1240000000000000000}, 3, 4},
-	{"12451", 3, dec{1250000000000000000}, 3, 5},
-	{"0", 0, nil, _WD, 0},
+	{"1235", 0, 0, dec{1235000000000000000}, _WD, 4},
+	{"1235", 0, 3, dec{1240000000000000000}, 3, 4},
+	{"1245", 0, 3, dec{1240000000000000000}, 3, 4},
+	{"12451", 0, 3, dec{1250000000000000000}, 3, 5},
+	{"0", 0, 0, nil, _WD, 0},
 }
 
 func TestDnorm(t *testing.T) {
@@ -58,7 +60,7 @@ func TestDnorm(t *testing.T) {
 func TestDecimal_SetInt(t *testing.T) {
 	for i, td := range intData {
 		t.Run(strconv.Itoa(i), func(t *testing.T) {
-			b, _ := new(big.Int).SetString(td.s, 0)
+			b, _ := new(big.Int).SetString(td.s, td.b)
 			d := new(Decimal).SetMode(ToNearestEven).SetPrec(td.p).SetInt(b)
 			if !reflect.DeepEqual(td.d, d.mant) {
 				t.Fatalf("\nexpected mantissa %v\n              got %v", td.d, d.mant)