stdlib: Add an interior vector version of sort and a test case

Author: pcwalton

src/lib/sort.rs

@@ -1,6 +1,9 @@
 
 import vec::len;
 import vec::slice;
+import ilen = ivec::len;
+import islice = ivec::slice;
+export ivector;
 export lteq;
 export merge_sort;
 export quick_sort;
@@ -130,6 +133,139 @@ fn quick_sort3[T](lteq[T] compare_func_lt, lteq[T] compare_func_eq,
     qsort3[T](compare_func_lt, compare_func_eq, arr, 0,
               (vec::len[T](arr) as int) - 1);
 }
+
+mod ivector {
+    export merge_sort;
+    export quick_sort;
+    export quick_sort3;
+
+    type lteq[T] = fn(&T, &T) -> bool;
+
+    fn merge_sort[T](lteq[T] le, &T[] v) -> T[] {
+        fn merge[T](lteq[T] le, &T[] a, &T[] b) -> T[] {
+            let T[] rs = ~[];
+            let uint a_len = ilen[T](a);
+            let uint a_ix = 0u;
+            let uint b_len = ilen[T](b);
+            let uint b_ix = 0u;
+            while (a_ix < a_len && b_ix < b_len) {
+                if (le(a.(a_ix), b.(b_ix))) {
+                    rs += ~[a.(a_ix)];
+                    a_ix += 1u;
+                } else { rs += ~[b.(b_ix)]; b_ix += 1u; }
+            }
+            rs += islice[T](a, a_ix, a_len);
+            rs += islice[T](b, b_ix, b_len);
+            ret rs;
+        }
+        let uint v_len = ilen[T](v);
+        if (v_len <= 1u) { ret v; }
+        let uint mid = v_len / 2u;
+        let T[] a = islice[T](v, 0u, mid);
+        let T[] b = islice[T](v, mid, v_len);
+        ret merge[T](le, merge_sort[T](le, a), merge_sort[T](le, b));
+    }
+
+    fn swap[T](&T[mutable] arr, uint x, uint y) {
+        auto a = arr.(x);
+        arr.(x) = arr.(y);
+        arr.(y) = a;
+    }
+
+    fn part[T](lteq[T] compare_func, &T[mutable] arr, uint left, uint right,
+               uint pivot) -> uint {
+        auto pivot_value = arr.(pivot);
+        swap[T](arr, pivot, right);
+        let uint storage_index = left;
+        let uint i = left;
+        while (i < right) {
+            if (compare_func({ arr.(i) }, pivot_value)) {
+                swap[T](arr, i, storage_index);
+                storage_index += 1u;
+            }
+            i += 1u;
+        }
+        swap[T](arr, storage_index, right);
+        ret storage_index;
+    }
+
+    fn qsort[T](lteq[T] compare_func, &T[mutable] arr, uint left,
+                uint right) {
+        if (right > left) {
+            auto pivot = (left + right) / 2u;
+            auto new_pivot = part[T](compare_func, arr, left, right, pivot);
+            if (new_pivot == 0u) { ret; }
+            qsort[T](compare_func, arr, left, new_pivot - 1u);
+            qsort[T](compare_func, arr, new_pivot + 1u, right);
+        }
+    }
+
+    fn quick_sort[T](lteq[T] compare_func, &T[mutable] arr) {
+        if (ilen[T](arr) == 0u) { ret; }
+        qsort[T](compare_func, arr, 0u, ilen[T](arr) - 1u);
+    }
+
+
+    // Based on algorithm presented by Sedgewick and Bentley here:
+    // http://www.cs.princeton.edu/~rs/talks/QuicksortIsOptimal.pdf
+    // According to these slides this is the algorithm of choice for
+    // 'randomly ordered keys, abstract compare' & 'small number of key values'
+    fn qsort3[T](lteq[T] compare_func_lt, lteq[T] compare_func_eq,
+                 &T[mutable] arr, int left, int right) {
+        if (right <= left) { ret; }
+        let T v = arr.(right);
+        let int i = left - 1;
+        let int j = right;
+        let int p = i;
+        let int q = j;
+        while (true) {
+            i += 1;
+            while (compare_func_lt({ arr.(i) }, v)) { i += 1; }
+            j -= 1;
+            while (compare_func_lt(v, { arr.(j) })) {
+                if (j == left) { break; }
+                j -= 1;
+            }
+            if (i >= j) { break; }
+            swap[T](arr, i as uint, j as uint);
+            if (compare_func_eq({ arr.(i) }, v)) {
+                p += 1;
+                swap[T](arr, p as uint, i as uint);
+            }
+            if (compare_func_eq(v, { arr.(j) })) {
+                q -= 1;
+                swap[T](arr, j as uint, q as uint);
+            }
+        }
+        swap[T](arr, i as uint, right as uint);
+        j = i - 1;
+        i += 1;
+        let int k = left;
+        while (k < p) {
+            swap[T](arr, k as uint, j as uint);
+            k += 1;
+            j -= 1;
+            if (k == ilen[T](arr) as int) { break; }
+        }
+        k = right - 1;
+        while (k > q) {
+            swap[T](arr, i as uint, k as uint);
+            k -= 1;
+            i += 1;
+            if (k == 0) { break; }
+        }
+        qsort3[T](compare_func_lt, compare_func_eq, arr, left, j);
+        qsort3[T](compare_func_lt, compare_func_eq, arr, i, right);
+    }
+
+    fn quick_sort3[T](lteq[T] compare_func_lt, lteq[T] compare_func_eq,
+                      &T[mutable] arr) {
+        if (ilen[T](arr) == 0u) { ret; }
+        qsort3[T](compare_func_lt, compare_func_eq, arr, 0,
+                  (ilen[T](arr) as int) - 1);
+    }
+}
+
 // Local Variables:
 // mode: rust;
 // fill-column: 78;

src/test/run-pass/lib-sort-ivec.rs

@@ -0,0 +1,28 @@
+// xfail-stage0
+
+use std;
+
+fn check_sort(&int[] v1, &int[] v2) {
+    auto len = std::ivec::len[int](v1);
+    fn lteq(&int a, &int b) -> bool { ret a <= b; }
+    auto f = lteq;
+    auto v3 = std::sort::ivector::merge_sort[int](f, v1);
+    auto i = 0u;
+    while (i < len) { log v3.(i); assert (v3.(i) == v2.(i)); i += 1u; }
+}
+
+fn main() {
+    {
+        auto v1 = ~[3, 7, 4, 5, 2, 9, 5, 8];
+        auto v2 = ~[2, 3, 4, 5, 5, 7, 8, 9];
+        check_sort(v1, v2);
+    }
+    { auto v1 = ~[1, 1, 1]; auto v2 = ~[1, 1, 1]; check_sort(v1, v2); }
+    { let int[] v1 = ~[]; let int[] v2 = ~[]; check_sort(v1, v2); }
+    { auto v1 = ~[9]; auto v2 = ~[9]; check_sort(v1, v2); }
+    {
+        auto v1 = ~[9, 3, 3, 3, 9];
+        auto v2 = ~[3, 3, 3, 9, 9];
+        check_sort(v1, v2);
+    }
+}