Optionals

An optional type X? can either contain a value of type X of no value, i.e. nil.

Usage

var optional: i32?   # no value, by default
optional = 13
optional = nil

🔥 Code can not refer to values contained in an optional directly, since it might not be present. Instead, we need to "unwrap" it safely:

var optional: i32?
for i in optional
    # i is the contained i32
    print(i + 20)
else
    print("no value")

Optionals can also be processed by data pipes, i.e. get unwrapped, transformed and wrapped again:

(2.0 as f32?) |> sin

🔥 We can also insist to use the value and risk a failure:

print(optional! + 5)

This will exit the program with an error message, if the values is not set.

We can also "catch" errors, and keep the program running:

try
    print(optional! + 5)
except
    print("...failed")

🔥 This is not a full exception system! It is simpler/faster, but exceptions can not pass function boundaries!

If we feel particulary sure of our code, we can even do this:

trust_me
    print(optional! + 5)

🔥🔥 No error checking! Might have freaky consequences, if no value is set!