Negate a value in place

Goal

Fill in NegateInPlace so it flips the sign of the int n points to, writing the result back through the pointer.

Example

x := 5
NegateInPlace(&x)
fmt.Println(x) // -5

NegateInPlace(&x)
fmt.Println(x) // 5

Rules

• Edit negate.go. The function has a // TODO comment and currently does nothing.
• Use *n to read and write the value n points to.
• Flip the sign with subtraction: 0 minus the value gives you the opposite sign.
• 0 negated is still 0.
• Do not change the line func NegateInPlace(n *int) {. Do not add imports.

What you'll practice

Writing a new value back through a pointer parameter, and using subtraction to flip a number's sign.

Run it

gonomicon fetch week-1/13-04-negate-in-place
cd 13-04-negate-in-place
gonomicon test
gonomicon submit

Hints

1. Negating a number means flipping its sign. Subtraction gets you there: 0 minus a number flips it to the opposite sign, since 0 - 5 = -5 and 0 - (-5) = 5.
2. You don't need an if to flip a sign. Subtract *n from 0 and write the result back through n, the same way earlier pointer functions wrote back an updated value.
3. *n = 0 - *n