Clean up error messages and shadowed types/vars (#63)

Also add a comment to explain the use of a struct to define `Decimal64`.

Author: shaneHowearth

decimal64.go

@@ -31,6 +31,7 @@ const (
 
 // Decimal64 represents an IEEE 754 64-bit floating point decimal number.
 // It uses the binary representation method.
+// Decimal64 is intentionally a struct to ensure users don't accidentally cast it to uint64
 type Decimal64 struct {
 	bits uint64
 }
@@ -241,8 +242,8 @@ func (d Decimal64) parts() (fl flavor, sign int, exp int, significand uint64) {
 
 // getParts gets the parts and returns in decParts stuct, doesn't get the magnitude due to performance issues\
 func (d Decimal64) getParts() decParts {
-	flavor, sign, exp, significand := d.parts()
-	return decParts{flavor, sign, exp, uint128T{significand, 0}, &d}
+	flav, sign, exp, significand := d.parts()
+	return decParts{flav, sign, exp, uint128T{significand, 0}, &d}
 }
 
 func expWholeFrac(exp int, significand uint64) (exp2 int, whole uint64, frac uint64) {
@@ -279,8 +280,8 @@ func expWholeFrac(exp int, significand uint64) (exp2 int, whole uint64, frac uin
 
 // Float64 returns a float64 representation of d.
 func (d Decimal64) Float64() float64 {
-	flavor, sign, exp, significand := d.parts()
-	switch flavor {
+	flav, sign, exp, significand := d.parts()
+	switch flav {
 	case flNormal:
 		if significand == 0 {
 			return 0.0 * float64(1-2*sign)
@@ -301,8 +302,8 @@ func (d Decimal64) Float64() float64 {
 
 // Int64 converts d to an int64.
 func (d Decimal64) Int64() int64 {
-	flavor, sign, exp, significand := d.parts()
-	switch flavor {
+	flav, sign, exp, significand := d.parts()
+	switch flav {
 	case flInf:
 		if sign == 0 {
 			return math.MaxInt64
@@ -327,38 +328,38 @@ func (d Decimal64) Int64() int64 {
 
 // IsZero returns true if the Decimal encodes a zero value.
 func (d Decimal64) IsZero() bool {
-	fl, _, _, significand := d.parts()
-	return significand == 0 && fl == flNormal
+	flav, _, _, significand := d.parts()
+	return significand == 0 && flav == flNormal
 }
 
 // IsInf returns true iff d = ±∞.
 func (d Decimal64) IsInf() bool {
-	flavor, _, _, _ := d.parts()
-	return flavor == flInf
+	flav, _, _, _ := d.parts()
+	return flav == flInf
 }
 
 // IsNaN returns true iff d is not a number.
 func (d Decimal64) IsNaN() bool {
-	flavor, _, _, _ := d.parts()
-	return flavor == flQNaN || flavor == flSNaN
+	flav, _, _, _ := d.parts()
+	return flav == flQNaN || flav == flSNaN
 }
 
 // IsQNaN returns true iff d is a quiet NaN.
 func (d Decimal64) IsQNaN() bool {
-	flavor, _, _, _ := d.parts()
-	return flavor == flQNaN
+	flav, _, _, _ := d.parts()
+	return flav == flQNaN
 }
 
 // IsSNaN returns true iff d is a signalling NaN.
 func (d Decimal64) IsSNaN() bool {
-	flavor, _, _, _ := d.parts()
-	return flavor == flSNaN
+	flav, _, _, _ := d.parts()
+	return flav == flSNaN
 }
 
 // IsInt returns true iff d is an integer.
 func (d Decimal64) IsInt() bool {
-	fl, _, exp, significand := d.parts()
-	switch fl {
+	flav, _, exp, significand := d.parts()
+	switch flav {
 	case flNormal:
 		_, _, frac := expWholeFrac(exp, significand)
 		return frac == 0
@@ -369,8 +370,8 @@ func (d Decimal64) IsInt() bool {
 
 // IsSubnormal returns true iff d is a subnormal.
 func (d Decimal64) IsSubnormal() bool {
-	fl, _, _, significand := d.parts()
-	return significand != 0 && significand < decimal64Base && fl == flNormal
+	flav, _, _, significand := d.parts()
+	return significand != 0 && significand < decimal64Base && flav == flNormal
 }
 
 // Sign returns -1/0/1 depending on whether d is </=/> 0.

decimal64fmt.go

@@ -30,11 +30,11 @@ func appendUint64(buf []byte, n, limit uint64) []byte {
 
 // Append appends the text representation of d to buf.
 func (d Decimal64) Append(buf []byte, format byte, prec int) []byte {
-	flavor, sign, exp, significand := d.parts()
+	flav, sign, exp, significand := d.parts()
 	if sign == 1 {
 		buf = append(buf, '-')
 	}
-	switch flavor {
+	switch flav {
 	case flQNaN, flSNaN:
 		return appendUint64(append(buf, []byte("NaN")...), significand, 10000)
 	case flInf:
@@ -64,10 +64,10 @@ formatBlock:
 		}
 		return buf
 	case 'f', 'F':
-		exp, whole, frac := expWholeFrac(exp, significand)
+		exponent, whole, frac := expWholeFrac(exp, significand)
 		if whole > 0 {
 			buf = appendUint64(buf, whole, decimal64Base)
-			for ; exp > 0; exp-- {
+			for ; exponent > 0; exponent-- {
 				buf = append(buf, '0')
 			}
 		} else {

decimal64math.go

@@ -129,8 +129,8 @@ func (ctx Context64) Quo(d, e Decimal64) Decimal64 {
 
 // Sqrt computes √d.
 func (d Decimal64) Sqrt() Decimal64 {
-	flavor, sign, exp, significand := d.parts()
-	switch flavor {
+	flav, sign, exp, significand := d.parts()
+	switch flav {
 	case flInf:
 		if sign == 1 {
 			return QNaN64

decimal64scan.go

@@ -79,7 +79,7 @@ func (d *Decimal64) Scan(state fmt.ScanState, verb rune) error {
 		return err
 	}
 	if len(dot) > 1 {
-		return fmt.Errorf("Too many dots")
+		return fmt.Errorf("too many dots")
 	}
 
 	frac, err := tokenString(state, unicode.IsDigit)
@@ -92,7 +92,7 @@ func (d *Decimal64) Scan(state fmt.ScanState, verb rune) error {
 		return err
 	}
 	if len(e) > 1 {
-		return fmt.Errorf("Too many 'e's")
+		return fmt.Errorf("too many 'e's")
 	}
 
 	var expSign int
@@ -107,13 +107,13 @@ func (d *Decimal64) Scan(state fmt.ScanState, verb rune) error {
 			return err
 		}
 		if exp == "" {
-			return fmt.Errorf("Exponent value missing")
+			return fmt.Errorf("exponent value missing")
 		}
 	}
 
 	mantissa := whole + frac
 	if mantissa == "" {
-		return fmt.Errorf("Mantissa missing")
+		return fmt.Errorf("mantissa missing")
 	}
 	mantissa = strings.TrimLeft(mantissa, "0")
 	if mantissa == "" {
@@ -143,7 +143,7 @@ func (d *Decimal64) Scan(state fmt.ScanState, verb rune) error {
 }
 
 func notDecimal64() error {
-	return fmt.Errorf("Not a valid Decimal64")
+	return fmt.Errorf("not a valid Decimal64")
 }
 
 func parseUint(s string) (int64, int) {
@@ -180,7 +180,7 @@ func scanSign(state fmt.ScanState) (int, error) {
 			return 1, nil
 		}
 	default:
-		return 0, fmt.Errorf("Too many +/- characters: %s", string(s))
+		return 0, fmt.Errorf("too many +/- characters: %s", string(s))
 	}
 	return 0, nil
 }