Can someone explain what .? is?

[hintron]

I'm not exactly sure what .? is - I get that it's checking if the value is null or not, but I don't understand what it returns - is it a bool? if so, how can it return two values as seen in half, ok := halve(2).?? I don't know if it's an operator used specifically for unions and/or Maybe, or if it's just . combined with the ternary (?) operator.

I am surprised that .? is used but not documented in the Odin overview or Odin example file.

[bymehul]

In Odin, .? is an optional/union extraction operator with type inference.

v.? returns two values:
(value, ok)

Where:

• value → extracted value
• ok → bool indicating success

Example:

halve :: proc(n: int) -> Maybe(int) {
    if n % 2 != 0 do return nil
    return n / 2
}

half, ok := halve(2).?

Result

If value exists:

half = 1
ok   = true

If value is nil:

half = 0      // default value of int
ok   = false

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