#ifndef _BLASR_STAT_UTILS_IMPL_HPP_
#define _BLASR_STAT_UTILS_IMPL_HPP_

#include <ctime>
#include <vector>

inline int Choose(int a, int b)
{
    // A quick choose for small values.
    assert(a >= b);
    if (a < FactorialTableLength and b < FactorialTableLength) {
        return (FactorialTable[a] / (FactorialTable[b] * FactorialTable[a - b]));
    } else {
        //
        // Less quick choose for numerically stable values.
        //
        unsigned long al = a, bl = b, fact = 0;
        fact = al;
        //
        // The full value of b! must be able to be computed.
        //
        if (b >= FactorialTableLength) {
            return 0;
        }
        while (al > bl) {
            --al;
            if (ULONG_MAX / al < fact) {
                // there is overflow in the computation of a!/(a-b)!
                return 0;
            } else {
                fact = fact * al;
            }
        }
        return fact / FactorialTable[b];
    }
}

template <typename T>
void MeanVar(std::vector<T> &values, float &mean, float &var)
{
    T sum = 0;
    T sumsq = 0;
    size_t i;
    if (values.size() == 0) {
        mean = 0;
        var = 0;
        return;
    }
    for (i = 0; i < values.size(); i++) {
        sum += values[i];
        sumsq += values[i] * values[i];
    }
    mean = (1.0 * sum) / values.size();
    var = sumsq / values.size() - (mean * mean);
}

#endif
