replace quicksort with blocksort

andrewrk · andrewrk · commit 75ecfdf66db2 · 2017-12-14T19:41:35.000-05:00
closes #657
diff --git a/std/math/index.zig b/std/math/index.zig
@@ -174,12 +174,6 @@ test "math" {
 }
 
 
-pub const Cmp = enum {
-    Less,
-    Equal,
-    Greater,
-};
-
 pub fn min(x: var, y: var) -> @typeOf(x + y) {
     if (x < y) x else y
 }
@@ -522,3 +516,28 @@ pub fn cast(comptime T: type, x: var) -> %T {
         return T(x);
     }
 }
+
+pub fn floorPowerOfTwo(comptime T: type, value: T) -> T {
+    var x = value;
+
+    comptime var i = 1;
+    inline while(T.bit_count > i) : (i *= 2) {
+        x |= (x >> i);
+    }
+
+    return x - (x >> 1);
+}
+
+test "math.floorPowerOfTwo" {
+    testFloorPowerOfTwo();
+    comptime testFloorPowerOfTwo();
+}
+
+fn testFloorPowerOfTwo() {
+    assert(floorPowerOfTwo(u32, 63) == 32);
+    assert(floorPowerOfTwo(u32, 64) == 64);
+    assert(floorPowerOfTwo(u32, 65) == 64);
+    assert(floorPowerOfTwo(u4, 7) == 4);
+    assert(floorPowerOfTwo(u4, 8) == 8);
+    assert(floorPowerOfTwo(u4, 9) == 8);
+}
diff --git a/std/math/sqrt.zig b/std/math/sqrt.zig
@@ -7,12 +7,34 @@
 
 const math = @import("index.zig");
 const assert = @import("../debug.zig").assert;
+const builtin = @import("builtin");
+const TypeId = builtin.TypeId;
 
-pub fn sqrt(x: var) -> @typeOf(x) {
+pub fn sqrt(x: var) -> (if (@typeId(@typeOf(x)) == TypeId.Int) @IntType(false, @typeOf(x).bit_count / 2) else @typeOf(x)) {
     const T = @typeOf(x);
-    switch (T) {
-        f32 => @inlineCall(sqrt32, x),
-        f64 => @inlineCall(sqrt64, x),
+    switch (@typeId(T)) {
+        TypeId.FloatLiteral => {
+            return T(sqrt64(x))
+        },
+        TypeId.Float => {
+            return switch (T) {
+                f32 => sqrt32(x),
+                f64 => sqrt64(x),
+                else => @compileError("sqrt not implemented for " ++ @typeName(T)),
+            };
+        },
+        TypeId.IntLiteral => comptime {
+            if (x > @maxValue(u128)) {
+                @compileError("sqrt not implemented for comptime_int greater than 128 bits");
+            }
+            if (x < 0) {
+                @compileError("sqrt on negative number");
+            }
+            return T(sqrt_int(u128, x));
+        },
+        TypeId.Int => {
+            return sqrt_int(T, x);
+        },
         else => @compileError("sqrt not implemented for " ++ @typeName(T)),
     }
 }
@@ -274,3 +296,35 @@ test "math.sqrt64.special" {
     assert(math.isNan(sqrt64(-1.0)));
     assert(math.isNan(sqrt64(math.nan(f64))));
 }
+
+fn sqrt_int(comptime T: type, value: T) -> @IntType(false, T.bit_count / 2) {
+    var op = value;
+    var res: T = 0;
+    var one: T = 1 << (T.bit_count - 2);
+
+    // "one" starts at the highest power of four <= than the argument.
+    while (one > op) {
+        one >>= 2;
+    }
+
+    while (one != 0) {
+        if (op >= res + one) {
+            op -= res + one;
+            res += 2 * one;
+        }
+        res >>= 1;
+        one >>= 2;
+    }
+
+    const ResultType = @IntType(false, T.bit_count / 2);
+    return ResultType(res);
+}
+
+test "math.sqrt_int" {
+    assert(sqrt_int(u32, 3) == 1);
+    assert(sqrt_int(u32, 4) == 2);
+    assert(sqrt_int(u32, 5) == 2);
+    assert(sqrt_int(u32, 8) == 2);
+    assert(sqrt_int(u32, 9) == 3);
+    assert(sqrt_int(u32, 10) == 3);
+}
diff --git a/std/mem.zig b/std/mem.zig
@@ -527,3 +527,40 @@ pub fn max(comptime T: type, slice: []const T) -> T {
 test "mem.max" {
     assert(max(u8, "abcdefg") == 'g');
 }
+
+pub fn swap(comptime T: type, a: &T, b: &T) {
+    const tmp = *a;
+    *a = *b;
+    *b = tmp;
+}
+
+/// In-place order reversal of a slice
+pub fn reverse(comptime T: type, items: []T) {
+    var i: usize = 0;
+    const end = items.len / 2;
+    while (i < end) : (i += 1) {
+        swap(T, &items[i], &items[items.len - i - 1]);
+    }
+}
+
+test "std.mem.reverse" {
+    var arr = []i32{ 5, 3, 1, 2, 4 };
+    reverse(i32, arr[0..]);
+
+    assert(eql(i32, arr, []i32{ 4, 2, 1, 3, 5 }))
+}
+
+/// In-place rotation of the values in an array ([0 1 2 3] becomes [1 2 3 0] if we rotate by 1)
+/// Assumes 0 <= amount <= items.len
+pub fn rotate(comptime T: type, items: []T, amount: usize) {
+    reverse(T, items[0..amount]);
+    reverse(T, items[amount..]);
+    reverse(T, items);
+}
+
+test "std.mem.rotate" {
+    var arr = []i32{ 5, 3, 1, 2, 4 };
+    rotate(i32, arr[0..], 2);
+
+    assert(eql(i32, arr, []i32{ 1, 2, 4, 5, 3 }))
+}
diff --git a/std/sort.zig b/std/sort.zig
