86 lines
2.1 KiB
Rust
86 lines
2.1 KiB
Rust
/// An enum representing the type of a piece.
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#[derive(Copy, Clone, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
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pub enum Piece {
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King,
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Queen,
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Rook,
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Bishop,
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Knight,
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Pawn,
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}
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impl Piece {
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/// The number of [Piece] variants.
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pub const NUM_VARIANTS: usize = 6;
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const ALL: [Self; Self::NUM_VARIANTS] = [
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Self::King,
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Self::Queen,
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Self::Rook,
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Self::Bishop,
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Self::Knight,
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Self::Pawn,
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];
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/// Iterate over all piece types.
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pub fn iter() -> impl Iterator<Item = Self> {
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Self::ALL.iter().cloned()
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}
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/// Convert from a piece index into a [Piece] type.
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///
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/// # Panics
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///
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/// Panics if the index is out of bounds.
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#[inline(always)]
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pub fn from_index(index: usize) -> Self {
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Self::try_from_index(index).expect("index out of bouds")
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}
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/// Convert from a piece index into a [Piece] type. Returns [None] if the index is out of
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/// bounds.
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pub fn try_from_index(index: usize) -> Option<Self> {
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if index < Self::NUM_VARIANTS {
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// SAFETY: we know the value is in-bounds
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Some(unsafe { Self::from_index_unchecked(index) })
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} else {
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None
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}
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}
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/// Convert from a piece index into a [Piece] type, no bounds checking.
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///
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/// # Safety
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///
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/// Should only be called with values that can be output by [Piece::index()].
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#[inline(always)]
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pub unsafe fn from_index_unchecked(index: usize) -> Self {
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std::mem::transmute(index as u8)
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}
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/// Return the index of a given [Piece].
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#[inline(always)]
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pub fn index(self) -> usize {
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self as usize
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}
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}
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#[cfg(test)]
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mod test {
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use super::*;
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#[test]
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fn from_index() {
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assert_eq!(Piece::from_index(0), Piece::King);
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assert_eq!(Piece::from_index(1), Piece::Queen);
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assert_eq!(Piece::from_index(5), Piece::Pawn);
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}
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#[test]
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fn index() {
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assert_eq!(Piece::King.index(), 0);
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assert_eq!(Piece::Queen.index(), 1);
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assert_eq!(Piece::Pawn.index(), 5);
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}
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}
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