mirror of
https://github.com/rust-lang/rust.git
synced 2024-12-05 13:13:40 +00:00
89 lines
2.3 KiB
Rust
89 lines
2.3 KiB
Rust
// check-pass
|
|
|
|
#![feature(adt_const_params, generic_const_exprs)]
|
|
#![allow(incomplete_features)]
|
|
|
|
mod lib {
|
|
const N_ISLANDS: usize = 4;
|
|
const N_BRIDGES: usize = 7;
|
|
const BRIDGES: [(usize, usize); 7] = [(0, 1), (0, 1), (0, 2), (0, 3), (0, 3), (1, 2), (2, 3)];
|
|
|
|
pub type Matrix = [[usize; N_ISLANDS]; N_ISLANDS];
|
|
|
|
const EMPTY_MATRIX: Matrix = [[0; N_ISLANDS]; N_ISLANDS];
|
|
|
|
const fn build(mut matrix: Matrix, (to, from): (usize, usize)) -> Matrix {
|
|
matrix[to][from] += 1;
|
|
matrix[from][to] += 1;
|
|
matrix
|
|
}
|
|
|
|
pub const fn walk(mut matrix: Matrix, from: usize, to: usize) -> Matrix {
|
|
matrix[from][to] -= 1;
|
|
matrix[to][from] -= 1;
|
|
matrix
|
|
}
|
|
|
|
const fn to_matrix(bridges: [(usize, usize); N_BRIDGES]) -> Matrix {
|
|
let matrix = EMPTY_MATRIX;
|
|
|
|
let matrix = build(matrix, bridges[0]);
|
|
let matrix = build(matrix, bridges[1]);
|
|
let matrix = build(matrix, bridges[2]);
|
|
let matrix = build(matrix, bridges[3]);
|
|
let matrix = build(matrix, bridges[4]);
|
|
let matrix = build(matrix, bridges[5]);
|
|
let matrix = build(matrix, bridges[6]);
|
|
|
|
matrix
|
|
}
|
|
|
|
const BRIDGE_MATRIX: [[usize; N_ISLANDS]; N_ISLANDS] = to_matrix(BRIDGES);
|
|
|
|
pub struct Walk<const CURRENT: usize, const REMAINING: Matrix> {
|
|
_p: (),
|
|
}
|
|
|
|
impl Walk<0, BRIDGE_MATRIX> {
|
|
pub const fn new() -> Self {
|
|
Self { _p: () }
|
|
}
|
|
}
|
|
|
|
impl<const CURRENT: usize, const REMAINING: Matrix> Walk<CURRENT, REMAINING> {
|
|
pub fn proceed_to<const NEXT: usize>(
|
|
self,
|
|
) -> Walk<NEXT, { walk(REMAINING, CURRENT, NEXT) }> {
|
|
Walk { _p: () }
|
|
}
|
|
}
|
|
|
|
pub struct Trophy {
|
|
_p: (),
|
|
}
|
|
|
|
impl<const CURRENT: usize> Walk<CURRENT, EMPTY_MATRIX> {
|
|
pub fn collect_prize(self) -> Trophy {
|
|
Trophy { _p: () }
|
|
}
|
|
}
|
|
}
|
|
|
|
pub use lib::{Trophy, Walk};
|
|
|
|
fn main() {
|
|
// Example, taking the first step
|
|
let _ = Walk::new().proceed_to::<1>();
|
|
|
|
// Don't be so eager to collect the trophy
|
|
// let trophy = Walk::new()
|
|
// .proceed_to::<1>()
|
|
// .proceed_to::<0>()
|
|
// .collect_prize();
|
|
|
|
// Can't just make a Trophy out of thin air, you must earn it
|
|
// let trophy: Trophy = Trophy { _p: () };
|
|
|
|
// Can you collect the Trophy?
|
|
}
|