fc6b7c8b38
Long lines were fixed in a very crude way, as I'll be following up with another reformat in a bit.
109 lines
3.3 KiB
Rust
109 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" <-- leaning toward this model
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or
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two functions, "return the number of possible edits" and "return edit #n"
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It would be nice if this could be data-driven, so the two functions 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 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 std::vec;
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import std::vec::slice;
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import std::vec::len;
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import std::int;
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fn vec_omit<@T>(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>(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>(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>(v: [T], i: uint) -> [T] { slice(v, 0u, i) }
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fn vec_suffix<@T>(v: [T], i: uint) -> [T] { slice(v, i, len(v)) }
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fn vec_poke<@T>(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>(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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iter ix(skip_low: uint, skip_high: uint, length: uint) -> uint {
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let i: uint = skip_low;
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while i + skip_high <= length { put i; i += 1u; }
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}
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// Returns a bunch of modified versions of v, some of which introduce new elements (borrowed from xs).
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fn vec_edits<@T>(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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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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edits += [vec::reversed(v)];
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}
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for each i: uint in ix(0u, 1u, Lv) { edits += [vec_omit(v, i)]; }
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for each i: uint in ix(0u, 1u, Lv) { edits += [vec_dup(v, i)]; }
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for each i: uint in ix(0u, 2u, Lv) { edits += [vec_swadj(v, i)]; }
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for each i: uint in ix(1u, 2u, Lv) { edits += [vec_prefix(v, i)]; }
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for each i: uint in ix(2u, 1u, Lv) { edits += [vec_suffix(v, i)]; }
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for each j: uint in ix(0u, 1u, len(xs)) {
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for each i: uint in ix(0u, 1u, Lv) {
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edits += [vec_poke(v, i, xs[j])];
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}
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for each i: uint in ix(0u, 0u, Lv) {
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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: 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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ret s + "]";
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}
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fn show_edits(a: [int], xs: [int]) {
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log_err "=== Edits of " + vec_to_str(a) + " ===";
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let b = vec_edits(a, xs);
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for each i: uint in ix(0u, 1u, len(b)) { log_err 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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