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#[macro_export]
macro_rules! __hidden_handling_cases {
(else $e: expr) => {$e};
($cond : expr => $if_true: expr;
$(elif $cond2: expr => $if_t2:expr;)*
else $if_false:expr
) => {
[__hidden_handling_cases!($($cond2 => $if_t2; )elif * else $if_false), $if_true][$cond as bool as usize]
};
}
#[macro_export]
macro_rules! const_if {
($cond: expr => $if_true:expr;$if_false: expr) => {
[$if_false, $if_true][(!!$cond) as usize]
};
($cond : expr => $if_true: expr;
$(elif $cond2: expr => $if_t2:expr;)*
else $if_false:expr
) => {
__hidden_handling_cases!($cond => $if_true; $(elif $cond2 => $if_t2;)* else $if_false)
};
}
mod tests {
const fn min(x: i32, y: i32) -> i32 {
const_if!(x < y => x;y)
}
#[test]
fn test_min() {
assert_eq!(min(2, 3), 2);
}
const fn is_zero(i: i32) -> &'static str {
const_if!(
i == 0 => "Yes";
else "No"
)
}
const fn compare_to_42(i: i32) -> &'static str {
const_if!(
i < 42 => "Lesser";
elif i == 42 => "Equals";
else "Bigger"
)
}
const fn int_to_str(i: i32) -> &'static str {
const_if!(
i == 0 => "Zero";
elif i == 1 => "One";
elif i == 2 => "Two";
elif i == 3 => "Three";
elif i == 4 => "Four";
elif i == 5 => "Five";
elif i == 6 => "Six";
elif i == 7 => "Seven";
elif i == 8 => "Eight";
elif i == 9 => "Nine";
elif i == 10 => "Ten";
else "Unknown"
)
}
#[test]
fn test_multiple_elif() {
assert_eq!(int_to_str(0), "Zero");
assert_eq!(int_to_str(5), "Five");
assert_eq!(int_to_str(10), "Ten");
assert_eq!(int_to_str(11), "Unknown");
}
#[test]
fn test_if_else() {
assert_eq!(is_zero(0), "Yes");
assert_eq!(is_zero(42), "No");
}
#[test]
fn test_if_elif_else() {
assert_eq!(compare_to_42(0), "Lesser");
assert_eq!(compare_to_42(42), "Equals");
assert_eq!(compare_to_42(1337), "Bigger");
}
#[test]
fn test_expanded() {
let i = 6;
assert_eq!(
[
[
[
[
[
[
[
[
[
[["Unknown", "Ten"][(i == 10) as usize], "Nine"]
[(i == 9) as usize],
"Eight",
][(i == 8) as usize],
"Seven",
][(i == 7) as usize],
"Six",
][(i == 6) as usize],
"Five",
][(i == 5) as usize],
"Four",
][(i == 4) as usize],
"Three",
][(i == 3) as usize],
"Two",
][(i == 2) as usize],
"One",
][(i == 1) as usize],
"Zero",
][(i == 0) as usize],
"Six"
);
}
}