113 lines
3.3 KiB
Rust
113 lines
3.3 KiB
Rust
/*
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Idea: provide functions for 'exhaustive' and 'random' modification of vecs.
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two functions, "return all edits" and "return a random edit" <--
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leaning toward this model or two functions, "return the number of
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possible edits" and "return edit #n"
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It would be nice if this could be data-driven, so the two functions
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could share information:
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type vec_modifier = rec(fn (<T> v, uint i) -> ~[T] fun, uint lo, uint di);
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const ~[vec_modifier] vec_modifiers = ~[rec(fun=vec_omit, 0u, 1u), ...]/~;
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But that gives me "error: internal compiler error unimplemented consts
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that's not a plain literal".
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https://github.com/graydon/rust/issues/570
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vec_edits is not an iter because iters might go away.
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*/
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use std;
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import vec;
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import vec::slice;
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import vec::len;
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import int;
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fn vec_omit<T: copy>(v: ~[T], i: uint) -> ~[T] {
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slice(v, 0u, i) + slice(v, i + 1u, len(v))
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}
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fn vec_dup<T: copy>(v: ~[T], i: uint) -> ~[T] {
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slice(v, 0u, i) + [v[i]] + slice(v, i, len(v))
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}
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fn vec_swadj<T: copy>(v: ~[T], i: uint) -> ~[T] {
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slice(v, 0u, i) + [v[i + 1u], v[i]] + slice(v, i + 2u, len(v))
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}
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fn vec_prefix<T: copy>(v: ~[T], i: uint) -> ~[T] { slice(v, 0u, i) }
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fn vec_suffix<T: copy>(v: ~[T], i: uint) -> ~[T] { slice(v, i, len(v)) }
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fn vec_poke<T: copy>(v: ~[T], i: uint, x: T) -> ~[T] {
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slice(v, 0u, i) + ~[x] + slice(v, i + 1u, len(v))
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}
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fn vec_insert<T: copy>(v: ~[T], i: uint, x: T) -> ~[T] {
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slice(v, 0u, i) + ~[x] + slice(v, i, len(v))
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}
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// Iterates over 0...length, skipping the specified number on each side.
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fn ix(skip_low: uint, skip_high: uint, length: uint, it: block(uint)) {
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let i: uint = skip_low;
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while i + skip_high <= length { it(i); i += 1u; }
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}
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// Returns a bunch of modified versions of v, some of which introduce
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// new elements (borrowed from xs).
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fn vec_edits<T: copy>(v: ~[T], xs: ~[T]) -> ~[~[T]] {
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let edits: ~[~[T]] = ~[];
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let Lv: uint = len(v);
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if Lv != 1u {
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// When Lv == 1u, this is redundant with omit.
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vec::push(edits, ~[]);
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}
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if Lv >= 3u {
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// When Lv == 2u, this is redundant with swap.
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vec::push(edits, vec::reversed(v));
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}
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ix(0u, 1u, Lv) {|i| edits += ~[vec_omit(v, i)]; }
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ix(0u, 1u, Lv) {|i| edits += ~[vec_dup(v, i)]; }
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ix(0u, 2u, Lv) {|i| edits += ~[vec_swadj(v, i)]; }
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ix(1u, 2u, Lv) {|i| edits += ~[vec_prefix(v, i)]; }
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ix(2u, 1u, Lv) {|i| edits += ~[vec_suffix(v, i)]; }
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ix(0u, 1u, len(xs)) {|j|
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ix(0u, 1u, Lv) {|i|
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vec::push(edits, vec_poke(v, i, xs[j]));
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}
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ix(0u, 0u, Lv) {|i|
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vec::push(edits, vec_insert(v, i, xs[j]));
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}
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}
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edits
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}
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// Would be nice if this were built in:
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// https://github.com/graydon/rust/issues/424
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fn vec_to_str(v: ~[int]) -> str {
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let i = 0u;
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let s = "[";
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while i < len(v) {
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s += int::str(v[i]);
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if i + 1u < len(v) { s += ", "; }
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i += 1u;
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}
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return s + "]";
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}
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fn show_edits(a: ~[int], xs: ~[int]) {
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log(error, "=== Edits of " + vec_to_str(a) + " ===");
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let b = vec_edits(a, xs);
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ix(0u, 1u, len(b)) {|i| log(error, vec_to_str(b[i])); }
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}
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fn demo_edits() {
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let xs = ~[7, 8];
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show_edits(~[], xs);
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show_edits(~[1], xs);
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show_edits(~[1, 2], xs);
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show_edits(~[1, 2, 3], xs);
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show_edits(~[1, 2, 3, 4], xs);
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}
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fn main() { demo_edits(); }
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