Binary Search of Elements lying within an Interval

Search all elements (in a sorted vector of n elem.) that lie within an interval. It runs in log(n).

Search the elements that are lying within a specified interval.
Search the indexes of all elements in x (sorted vector of n elements) that lie within the interval.
The algorithm uses binary searches, thus it runs in log(n)
INPUT:
x: vector of numeric values sorted in ascending order
(e.g. 2,7,20,...120)
ref: numeric value of the reference point (center of the interval)
tol: numeric value corresponding to 1/2 of the width of the interval
The fourth input argument: numeric value (optional). Allows to define the maximum number of elements of x that can lie within the specified interval. This is useful in order to speed up the search.

OUTPUT:
indexes: indexes of elements of x which lie within the interval [ref-tol ref+tol]
If ref is not found in x then indexes is empty.