Simulated annealing code

[rose jacinth]

#pragma once

#include <cmath>
#include <random>
#include <utility>
#include <algorithm>

// To find a status with lower energy according to the given condition
template<typename status, typename count, typename energy_function, typename temperature_function, typename next_function, typename generator>
status simulated_annealing(status i_old, count c, const energy_function& ef, const temperature_function& tf, const next_function& nf, generator& g){

    auto   e_old  = ef(i_old);

    status i_best = i_old;
    auto   e_best = e_old;

    std::uniform_real_distribution<decltype(e_old)> rf(0, 1);

    for(; c > 0; --c){
        status i_new = nf(i_old, g);
        auto   e_new = ef(i_new);

        if(e_new < e_best){
            i_best =           i_new ;
            e_best =           e_new ;
        }

        if( e_new < e_old || std::exp( (e_old - e_new) / tf(c) ) > rf(g) ){
            i_old  = std::move(i_new);
            e_old  = std::move(e_new);
        }
    }
    return(i_best);
}

[versed spear]

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[rose jacinth]

Can anyone explain this line of code from https://codereview.stackexchange.com/questions/70310/simple-simulated-annealing-template-in-c11?
std::uniform_real_distribution<decltype(e_old)> rf(0, 1);