Binary search is an algorithm that looks for an element in a sorted data-structure by constantly dividing the search space in half.

###[Rosetta Code][1]

> A binary search divides a range of values into halves, and continues to narrow down the field of search until the unknown value is found. It is the classic example of a "divide and conquer" algorithm.

###[Wikipedia][2]
> In computer science, a binary search or half-interval search algorithm finds the position of a target value within a sorted array. The binary search algorithm can be classified as a dichotomic divide-and-conquer search algorithm and executes in logarithmic time.

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Smallest # of bytes wins

Clarifications:

  - Example of calling the function/lambda/macro should be included, but don't count those chars!
  - Output should be `> -1` if found, and `<=-1` otherwise

### Example

    > binary_search([1,2,3,4,5,6,7,8,9,10], 5);
    4
    > binary_search([1,2,3,4,5,6,7,8,9,10], 543);
    -1

  [1]: http://rosettacode.org/wiki/Binary_search
  [2]: https://en.wikipedia.org/wiki/Binary_search_algorithm