title: Generate random list of numbers that add up to 1
body: <p>Are there any STL functions that allow one to create a vector with random numbers that add up to 1? Ideally, this would be dependent on the size of the vector, so that I can make the vector size, say, 23 and this function will populate those 23 elements with random numbers between 0 and 1 that all add up to 1.</p>