error handling and tidying

1 files changed, 16 insertions, 14 deletions

diff --git a/op.go b/op.go
index ab57a84..6ccc6a8 100644
--- a/op.go
+++ b/op.go
@@ -5,39 +5,41 @@ import (
 	"math"
 )
 
-// parseOp returns a closure that performs the specified arithmetic operation,
+// parseOperator returns a closure that performs the specified arithmetic operation,
 // or OpError if op is not a valid operator.
-func parseOp(op byte) (func(lhs *float64, rhs float64), error) {
+func parseOperator(op byte) (func(lhs float64, rhs float64) float64, error) {
 	switch op {
 	case '+':
-		return func(lhs *float64, rhs float64) { *lhs += rhs }, nil
+		return func(lhs, rhs float64) float64 { return lhs + rhs }, nil
 	case '-':
-		return func(lhs *float64, rhs float64) { *lhs -= rhs }, nil
+		return func(lhs, rhs float64) float64 { return lhs - rhs }, nil
 	case '*':
-		return func(lhs *float64, rhs float64) { *lhs *= rhs }, nil
+		return func(lhs, rhs float64) float64 { return lhs * rhs }, nil
 	case '/':
-		return func(lhs *float64, rhs float64) {
+		return func(lhs, rhs float64) float64 {
 			if rhs != 0 {
-				*lhs /= rhs
+				return lhs / rhs
 			}
+			return lhs
 		}, nil
 	case '%':
-		return func(lhs *float64, rhs float64) {
+		return func(lhs, rhs float64) float64 {
 			if rhs != 0 {
-				*lhs = float64(int64(*lhs) % int64(rhs))
+				return float64(int64(lhs) % int64(rhs))
 			}
+			return lhs
 		}, nil
 	case '^':
-		return func(lhs *float64, rhs float64) { *lhs = math.Pow(*lhs, rhs) }, nil
+		return func(lhs, rhs float64) float64 { return math.Pow(lhs, rhs) }, nil
 	}
-	return nil, OpError{op}
+	return nil, OperatorErr{op}
 }
 
-// OpError records an invalid arithmetic operator.
-type OpError struct {
+// OperatorErr records an invalid arithmetic operator.
+type OperatorErr struct {
 	c byte
 }
 
-func (e OpError) Error() string {
+func (e OperatorErr) Error() string {
 	return fmt.Sprintf("invalid operator: %c", e.c)
 }