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package main
import (
"fmt"
"math"
)
// parseOp 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) {
switch op {
case '+':
return func(lhs *float64, rhs float64) { *lhs += rhs }, nil
case '-':
return func(lhs *float64, rhs float64) { *lhs -= rhs }, nil
case '*':
return func(lhs *float64, rhs float64) { *lhs *= rhs }, nil
case '/':
return func(lhs *float64, rhs float64) {
if rhs != 0 {
*lhs /= rhs
}
}, nil
case '%':
return func(lhs *float64, rhs float64) {
if rhs != 0 {
*lhs = float64(int64(*lhs) % int64(rhs))
}
}, nil
case '^':
return func(lhs *float64, rhs float64) { *lhs = math.Pow(*lhs, rhs) }, nil
}
return nil, OpError{op}
}
// OpError records an invalid arithmetic operator.
type OpError struct {
c byte
}
func (e OpError) Error() string {
return fmt.Sprintf("invalid operator: %c", e.c)
}
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