Builtin for checking if vec contains specified element

Question

Let's say, I have a vec<int> containing a list of integers that may be non-continuous (due to element being removed from database).

Example:

$occupiedNumbers = vec[1, 2, 3, 5, 6, 8, 10, 11, 12, 13, 15, 16];

Now what I need is to check if this vec contains a given number, and if yes, increase it by 1 and repeat checking.

$newItemNumber = count($occupiedNumbers);
while (/* check if $occupiedNumbers contains $newItemNumber */) {
    $a++;
}

In vanilla PHP there is in_array() for this, but would that work for a vec? Also, there is a builtin HH\Vector::linearSearch() but it's meant to be used with vec's predecessor, HH\Vector.

What is the right solution to check if a vec contains a given value?

Neither HHVM nor Hack docs say about that use case for a vec. Also, I'm missing some sort of REPL tool to check it manually off-project without building a whole (possibly faulty) project.

Answer 1

The recommendation from the HHVM/HackLang guys is to use C\contains() as you can read here but you need to install the HSL package (hhvm/hsl) using composer. This library contains loads of functions to deal with the new array-type structures: vec, dict, keyset. Those functions in the HSL Library are prefixed with C, Vec, Dict, Keyset and you'll find also Math, Str, etc., very useful for other needs.

After installing that package it becomes available but typically it is more handy to add use namespace to avoid the long prefix:

use namespace HH\Lib\C;

This is how you can do it:

$exists = C\contains($occupiedNumbers, $newItemNumber);

Answer 2

If you are really looking for the longest continuous interval starting from count($occupiedNumbers) then it may be much faster to find its initial index in the sorted list (if it exists), then use direct indexing from there:

// `use namespace HH\Lib\{C, Vec};` at top level
$occupiedNumbers = vec[1, 2, 3, 5, 6, 8, 10, 11, 12, 13, 15, 16];

$sorted = Vec\sort($occupiedNumbers); // if not sorted in general
$size = count($sorted);
$v = $size;
$i = C\find_key($sorted, $w ==> $w === $v);
if($i !== null) {
  for(; $i < $size - 1 && $sorted[$i + 1] === $v + 1; $i++, $v++) {
  }
}
// $i is null | <index of largest number in continuous interval>