lab4 with peek

#include <iostream>
#include <fstream>
#include <string>

void name_file (std::string &input_string1, std::string &input_string2, std::string &output_string);
void sort_input (std::ifstream &input_file1, std::ifstream &input_file2, std::ofstream &output_file);
void set_input_name (std::ifstream &input, std::string input_name);
void set_output_name (std::ofstream &output, std::string output_name);
void close_file_input(std::ifstream &close);
void close_file_output(std::ofstream &close);

int main ()
{
    std::ifstream input_file1, input_file2;
    std::ofstream output_file;

    std::string input_filename1;
    std::string input_filename2;
    std::string output_filename;

    name_file(input_filename1, input_filename2, output_filename);
    set_output_name(output_file, output_filename);
    set_input_name(input_file1, input_filename1);
    set_input_name(input_file2, input_filename2);

    sort_input(input_file1, input_file2, output_file);

    close_file_input(input_file1);
    close_file_input(input_file2);
    close_file_output(output_file);

    std::cout << "The merger of the files is complete." << std::endl;

    return 0;
}


void name_file(std::string &input_string1, std::string &input_string2, std::string &output_string)
{
    //name the ouput file
    std::cout << "Including the file extension, please enter the name of the desired output file: ";
    std::cin >> output_string;

    //name the first input file
    std::cout << "What is the name of the first input file?  Please include the file extension: ";
    std::cin >> input_string1;

    //name the second input file
    std::cout << "What is the name of the second input file?  Please include the file extension: ";
    std::cin >> input_string2;
}

void set_input_name (std::ifstream &input, std::string input_name)
{
    //open file
    input.open(input_name.c_str());

    if (input.fail())
    {
        std::cout << "Error opening input file " << input_name << "." << std::endl;
    }
}

void set_output_name (std::ofstream &output, std::string output_name)
{
    //open file
    output.open(output_name.c_str(), std::ios::app);

    if (output.fail())
    {
        std::cout << "Error opening output file " << output_name << "." << std::endl;
    }
}

void close_file_input(std::ifstream &close)
{
    close.close();
}

void close_file_output(std::ofstream &close)
{
    close.close();
}

void sort_input (std::ifstream &input_file1, std::ifstream &input_file2, std::ofstream &output_file)
{
    //storage for input ints coming from two files
    int num1;
    int num2;
    char check1;
    char check2;

    //check to make sure first input is a number
    check1 = input_file1.peek();
    check2 = input_file2.peek();

    while(!(isdigit(check1)))
    {
        check1 = input_file1.get();
        check1 = input_file1.peek();
    }

    if(isdigit(check1))
    {
       input_file1 >> num1;
    }

    while(!(isdigit(check2)))
    {
        check2 = input_file2.get();
        check2 = input_file2.peek();
    }

    if(isdigit(check2))
    {
        input_file2 >> num2;
    }

    do
    {
        if(num2 < num1)
        {
            output_file << num2 << " " << std::endl;

            while(!(isdigit(check2)))
            {
                check2 = input_file2.get();
                check2 = input_file2.peek();
            }

            if(isdigit(check2))
            {
                input_file2 >> num2;
            }
            goto next;
        }

        if(num1 < num2)
        {
            output_file << num1 << " " << std::endl;

            while(!(isdigit(check1)))
            {
                check2 = input_file1.get();
                check2 = input_file1.peek();
            }

            if(isdigit(check1))
            {
                input_file1 >> num1;
            }
            goto next;
        }

        if(num1 == num2)
        {
            output_file << num1 << " " << num2 << " " << std::endl;

            while(!(isdigit(check1)))
            {
                check2 = input_file1.get();
                check2 = input_file1.peek();
            }

            if(isdigit(check1))
            {
                input_file1 >> num1;
            }

             while(!(isdigit(check2)))
            {
                check2 = input_file2.get();
                check2 = input_file2.peek();
            }

            if(isdigit(check2))
            {
                input_file2 >> num2;
            }
        }

        next:;

    }while ((!input_file1.eof()) && (!input_file2.eof()));

    if(input_file2.eof())
    {
        if(num2 < num1)
        {
            output_file << num2 << " " << std::endl;
        }

        else if (num1 == num2)
        {
            output_file << num1 << " " << num2 << " " << std::endl;
        }

        else
        {
            output_file << num1 << " " << std::endl;
        }

        while(!input_file1.eof())
        {
            check1 = input_file1.peek();

            if(isdigit(check1))
            {
                if(input_file1 >> num1)
                {
                    output_file << num1 << " " << std::endl;
                }
            }

            else
            {
                check1 = input_file1.get();
            }
        }

        output_file << num1 << " " << std::endl;
    }

    if(input_file1.eof())
    {
        if(num1 < num2)
        {
            output_file << num1 << " " << std::endl;
        }

        else if (num1 == num2)
        {
            output_file << num1 << " " << num2 << " " << std::endl;
        }

        else
        {
            output_file << num2 << " " << std::endl;
        }

        while(!input_file2.eof())
        {
            check1 = input_file2.peek();

            if(isdigit(check2))
            {
                if(input_file2 >> num1)
                {
                    output_file << num2 << " " << std::endl;
                }
            }

            else
            {
                check2 = input_file2.get();
            }
        }

        output_file << num2 << " " << std::endl;
    }

    /*if(input_file1.eof())
    {
        if(num1 < num2)
        {
            output_file << num1 << " " << std::endl;
        }

        else if (num1 == num2)
        {
            output_file << num1 << " " << num2 << " " << std::endl;
        }

        while(input_file2 >> num2)
        {
            output_file << num2 << " " << std::endl;
        }
    }
    */

    input_file1.clear();
    input_file2.clear();
    output_file.clear();
}