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Change API for binarySearch fn

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This commit is contained in:
LemonBoy 2020-02-03 14:42:32 +01:00
parent fd8d8afb24
commit db3aea3a0b
1 changed files with 17 additions and 18 deletions
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35
lib/std/sort.zig
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@ -5,7 +5,7 @@ const mem = std.mem;
const math = std.math;
const builtin = @import("builtin");
pub fn binarySearch(comptime T: type, items: []T, comptime compareFn: fn (val: T) math.Order) ?usize {
pub fn binarySearch(comptime T: type, key: T, items: []const T, comptime compareFn: fn (lhs: T, rhs: T) math.Order) ?usize {
if (items.len < 1)
return null;
@ -15,11 +15,11 @@ pub fn binarySearch(comptime T: type, items: []T, comptime compareFn: fn (val: T
while (left <= right) {
// Avoid overflowing in the midpoint calculation
const mid = left + (right - left) / 2;
// Compare the midpoint element with the key
switch (compareFn(items[mid])) {
// Compare the key with the midpoint element
switch (compareFn(key, items[mid])) {
.eq => return mid,
.lt => left = mid + 1,
.gt => right = mid - 1,
.gt => left = mid + 1,
.lt => right = mid - 1,
}
}
@ -28,41 +28,40 @@ pub fn binarySearch(comptime T: type, items: []T, comptime compareFn: fn (val: T
test "std.sort.binarySearch" {
const S = struct {
fn makeComparisonPred(comptime T: type, value: T) type {
return struct {
fn pred(v: T) math.Order {
return math.order(v, value);
}
};
fn order_u32(lhs: u32, rhs: u32) math.Order {
return math.order(lhs, rhs);
}
fn order_i32(lhs: i32, rhs: i32) math.Order {
return math.order(lhs, rhs);
}
};
testing.expectEqual(
@as(?usize, null),
binarySearch(u32, &[_]u32{}, S.makeComparisonPred(u32, 1).pred),
binarySearch(u32, 1, &[_]u32{}, S.order_u32),
);
testing.expectEqual(
@as(?usize, 0),
binarySearch(u32, &[_]u32{1}, S.makeComparisonPred(u32, 1).pred),
binarySearch(u32, 1, &[_]u32{1}, S.order_u32),
);
testing.expectEqual(
@as(?usize, null),
binarySearch(u32, &[_]u32{0}, S.makeComparisonPred(u32, 1).pred),
binarySearch(u32, 1, &[_]u32{0}, S.order_u32),
);
testing.expectEqual(
@as(?usize, 4),
binarySearch(u32, &[_]u32{ 1, 2, 3, 4, 5 }, S.makeComparisonPred(u32, 5).pred),
binarySearch(u32, 5, &[_]u32{ 1, 2, 3, 4, 5 }, S.order_u32),
);
testing.expectEqual(
@as(?usize, 0),
binarySearch(u32, &[_]u32{ 2, 4, 8, 16, 32, 64 }, S.makeComparisonPred(u32, 2).pred),
binarySearch(u32, 2, &[_]u32{ 2, 4, 8, 16, 32, 64 }, S.order_u32),
);
testing.expectEqual(
@as(?usize, 1),
binarySearch(i32, &[_]i32{ -7, -4, 0, 9, 10 }, S.makeComparisonPred(i32, -4).pred),
binarySearch(i32, -4, &[_]i32{ -7, -4, 0, 9, 10 }, S.order_i32),
);
testing.expectEqual(
@as(?usize, 3),
binarySearch(i32, &[_]i32{ -100, -25, 2, 98, 99, 100 }, S.makeComparisonPred(i32, 98).pred),
binarySearch(i32, 98, &[_]i32{ -100, -25, 2, 98, 99, 100 }, S.order_i32),
);
}