pattern-matching.swift

/// Ignores `value` and just evaluates `pattern`.
/// Can be used to evaluate arbitrary expressions in a switch.
func ~=<A>(pattern: @autoclosure () -> Bool, value: A) -> Bool {
    return pattern()
}

let (x, y, z) = (0, 0, 1)

switch () /* can be anything */ {
case x > 0: print("x matches")
case y < 0: print("y matches")
case z == 1: print("z matches")
default: print("no match")
}