Basics of pointers

A pointer to a variable is the address of that variable in memory.

Unlike C++, Go doesn’t allow pointer arithmetic i.e. you can’t add or substract from pointers.

Zero value of a pointer is nil.

// We'll show how pointers work in contrast to values with
// 2 functions: `zeroval` and `zeroptr`. `zeroval` has an
// `int` parameter, so arguments will be passed to it by
// value. `zeroval` will get a copy of `ival` distinct
// from the one in the calling function.
func zeroval(ival int) {
	ival = 0
}

// `zeroptr` in contrast has an `*int` parameter, meaning
// that it takes an `int` pointer. The `*iptr` code in the
// function body then _dereferences_ the pointer from its
// memory address to the current value at that address.
// Assigning a value to a dereferenced pointer changes the
// value at the referenced address.
func zeroptr(iptr *int) {
	*iptr = 0
}

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Once these functions are defined, you can do the following:

i := 1
fmt.Println("initial:", i)

zeroval(i)
fmt.Println("zeroval:", i)
// `i` is still equal to 1 because `zeroval` edited
// a "copy" of `i`, not the original.

// The `&i` syntax gives the memory address of `i`,
// i.e. a pointer to `i`. When calling `zeroptr`,
// it will edit the "original" `i`.
zeroptr(&i)
fmt.Println("zeroptr:", i)

// Pointers can be printed too.
fmt.Println("pointer:", &i)

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initial: 1
zeroval: 1
zeroptr: 0
pointer: 0xc00007c010

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