Macro example 

macro_rules! example {
    (
        title: $title:expr,
        source: $source:expr,
        input: $input:expr,
        result: $result:expr $(,)?
    ) => { ... };
    (
        title: $title:expr,
        source: $source:expr,
        result: $result:expr $(,)?
    ) => { ... };
    (
        title: $title:expr,
        source: $source:expr,
        result: $result:expr,
        deterministic: $det:expr $(,)?
    ) => { ... };
}

Macro to create an Example with automatic source location tracking