A simple macro to emulate a switch statement in Rust.
The switch! macro looks similar to match. But instead of pattern matching,
each left-hand-side expression is interpreted as an expression instead of a
pattern. One use case for this is to match against constants joined with
bitwise OR. The output of the macro is a match with if guards.
```rust const A: u32 = 1 << 0; const B: u32 = 1 << 1; const C: u32 = 1 << 2;
fn flag_string(input: u32) -> &'static str { switch! { input; A => "A", // bitwise OR A | B => "A and B", A | B | C => "A and B and C", B | C => "B and C", _ => "other" } } ```
The above code expands to:
```rust const A: u32 = 1 << 0; const B: u32 = 1 << 1; const C: u32 = 1 << 2;
fn flag_string(input: u32) -> &'static str { match input { v if v == A => "A", v if v == A | B => "A and B", v if v == A | B | C => "A and B and C", v if v == B | C => "B and C", _ => "other" } } ```