59 lines
1.2 KiB
Rust
59 lines
1.2 KiB
Rust
// run-pass
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// If `Index` used an associated type for its output, this test would
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// work more smoothly.
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use std::ops::Index;
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struct Mat<T> { data: Vec<T>, cols: usize, }
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impl<T> Mat<T> {
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fn new(data: Vec<T>, cols: usize) -> Mat<T> {
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Mat { data: data, cols: cols }
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}
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fn row<'a>(&'a self, row: usize) -> Row<&'a Mat<T>> {
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Row { mat: self, row: row, }
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}
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}
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impl<T> Index<(usize, usize)> for Mat<T> {
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type Output = T;
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fn index<'a>(&'a self, (row, col): (usize, usize)) -> &'a T {
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&self.data[row * self.cols + col]
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}
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}
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impl<'a, T> Index<(usize, usize)> for &'a Mat<T> {
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type Output = T;
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fn index<'b>(&'b self, index: (usize, usize)) -> &'b T {
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(*self).index(index)
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}
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}
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struct Row<M> { mat: M, row: usize, }
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impl<T, M: Index<(usize, usize), Output=T>> Index<usize> for Row<M> {
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type Output = T;
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fn index<'a>(&'a self, col: usize) -> &'a T {
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&self.mat[(self.row, col)]
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}
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}
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fn main() {
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let m = Mat::new(vec![1, 2, 3, 4, 5, 6], 3);
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let r = m.row(1);
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assert_eq!(r.index(2), &6);
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assert_eq!(r[2], 6);
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assert_eq!(r[2], 6);
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assert_eq!(6, r[2]);
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let e = r[2];
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assert_eq!(e, 6);
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let e: usize = r[2];
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assert_eq!(e, 6);
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}
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