Switch Statement For Rust
A simple macro to emulate a switch statement in Rust.
Description
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.
Example
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:
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"
}
}