The following functions are used by the access and update routines to locate the bin which corresponds to a given x coordinate.
This function finds and sets the index i to the bin number which
covers the coordinate x in the histogram h. The bin is
located using a binary search. The search includes an optimization for
histograms with uniform range, and will return the correct bin
immediately in this case. If x is found in the range of the
histogram then the function sets the index i and returns
GSL_SUCCESS. If x lies outside the valid range of the
histogram then the function returns
GSL_EDOM and the error
handler is invoked.