Macro match_all::match_all

macro_rules! match_all {
    ($val:expr, IfNoMatch => $c:expr, $($($p:pat)|+ => $b:expr),+) => { ... };
    ($val:expr, $($($p:pat)|+ => $b:expr),+) => { ... };
}

match_all

Provides the match_all! macro for rust

This macro provides similar functionality to a vanilla match statement but allows for multiple expression blocks to be executed.

Format

match_all!{ value,
    IfNoMatch => expr,
    pat | pat ... => expr,
    ...
}

• value: the expression to match on.
• IfNoMatch: the expression after this is executed if none of the other patterns are matched. This branch is optional.
• pat | pat ...: this is groupings of patterns that will be checked. If any of them match to value then their corresponding expression is executed. After checking a group of patterns then the next group is checked until all groups have been checked. If none match then the IfNoMatch expression will be executed.

Example One

let value = Some(4);

match_all!{ value,
    None => println!("Hi"),
    Some(3) | Some(4) => println!("Hello"),
    Some(4) | Some(5) => println!("Howdy")
}

This would print:

Hello
Howdy

Example Two

let value = Some(20);
match_all!{ value,
    IfNoMatch => println!("No Match"),
    0...4 => println!("0 through 4")
};

This would print:

No Match

It prints this because it uses the special IfNoMatch expression to provide an expression that matches only when no other expression was matched.

Example Three

Desugaring match all

let value = Some(4);

match_all!{ value,
    None => println!("Hi"),
    Some(3) | Some(4) => println!("Hello"),
    Some(4) | Some(5) => println!("Howdy")
}

===

let value = Some(4);

if value == None {
    println!("Hi");
}
if value == Some(3) || value == Some(4) {
    println!("Hello");
}
if value == Some(4) || value == Some(5) {
    println!("Howdy");
}

Example Four

Desugaring match all

let value = Some(4);

match_all!{ value,
    IfNoMatch => println!("no match"),
    Some(3) | Some(4) => println!("Hello"),
    Some(4) | Some(5) => println!("Howdy")
}

===

let value = Some(4);
let matched = false;

if value == Some(3) || value == Some(4) {
    println!("Hello");
    matched = true;
}
if value == Some(4) || value == Some(5) {
    println!("Howdy");
    matched = true;
}
if !matched {
    println!("no match");
}