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pub type Bitboard = u64;
/// Print bitboard on screen in the same way squares appear in memory
/// (i.e the board is actually flipped along X)
#[allow(dead_code)]
pub fn print(bb: Bitboard) {
for index in 0..64 {
print!("{}", if bb >> index & 1 == 1 { "1" } else { "." });
if (index + 1) % 8 == 0 {
println!();
}
}
return println!();
}
/// Return bitboard cardinality, aka number of elements in the set
pub fn pop_count(bb: Bitboard) -> u8 {
if bb == 0 {
return 0;
}
return pop_count(bb >> 1) + (bb & 1) as u8;
}
/// Return Bitboard with only Least Single Bit
pub fn ls1b(bb: Bitboard) -> u64 {
bb & !(bb - 1)
}
/// Log base 2 (aka Trailing Zero Count)
///
/// WARNING: Only works for SINGLE Bitboards
/// Useful for calculating bit-index of LS1B
pub fn bitscan(bb: Bitboard) -> u8 {
debug_assert!(pop_count(bb) == 1, "Bitscan only works for SINGLE Bitboards!");
pop_count(bb - 1)
}
/// Aliases to board square indexes
#[allow(dead_code)]
enum Square {
A1, B1, C1, D1, E1, F1, G1, H1,
A2, B2, C2, D2, E2, F2, G2, H2,
A3, B3, C3, D3, E3, F3, G3, H3,
A4, B4, C4, D4, E4, F4, G4, H4,
A5, B5, C5, D5, E5, F5, G5, H5,
A6, B6, C6, D6, E6, F6, G6, H6,
A7, B7, C7, D7, E7, F7, G7, H7,
A8, B8, C8, D8, E8, F8, G8, H8,
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test_pop_count() {
assert_eq!(pop_count(127), 7);
}
#[test]
fn test_ls1b() {
assert_eq!(ls1b(38), 2);
assert_eq!(ls1b(16), 16);
assert_eq!(ls1b(20), 4);
}
#[test]
fn test_bitscan() {
assert_eq!(bitscan(4), 2);
assert_eq!(bitscan(16), 4);
assert_eq!(bitscan(64), 6);
assert_eq!(bitscan(128), 7);
}
#[test]
#[should_panic(expected = "Bitscan only works for SINGLE Bitboards!")]
fn test_bitscan_with_non_single_bb() {
bitscan(5);
}
#[test]
fn test_square_enum() {
assert_eq!(Square::A1 as u8, 0);
assert_eq!(Square::F1 as u8, 5);
assert_eq!(Square::H8 as u8, 63);
}
}
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