need c++ direction, gcd read from file

[kyyleofthemist]

alright, i have this project i'm working on where one needs to read several numbers from a file and find their gcd two numbers at a time.

for example

first two numbers on the file are 43 and 5 which when read need to output:
43 5
56 4 (etc.)
with a space between them (important)
when the program calculates the gcd of the two numbers, the output needs to be
43 5 1
56 4 4
etc.

i have the algorithm for gcd, but have no idea how to read from file, put spaces, read two numbers at a time and then have the gcd algorithm calculate the gcd for those given numbers and then put them in that desired output.


even further, i need to have these numbers and output files placed into its own separate file. which of course, i have no idea how to do.

if anyone can point or hint (not asking you to do work for me) on the correct direction i need to take to do this project, i will be so grateful.
like i said, i have no idea where to start.
i know how to open a file, close a file, but i don't really understand how i am supposed to read two numbers at a time...and calc gcd and output like that specifically.

thank you so much in advance if anyone reads this. i'm backed into a corner and on the ropes.

[hamsterman]

input/output with files is just like cin and cout.
This is how you'd read two numbers, and then write them, and the gcd into another file.

//open input_file
//open output_file
while(!input_file.eof()){
   int n1, n2;
   input_file >> n1 >> n2;
   output_file << n1 << ' ' << n2 << ' ' << gcd(n1, n2) << '\n';
}
//close files 

[filipe]

For better error checking, it's best to loop on the stream itself because it could go into a failure state (fail() or bad()):

while(input_file)
{
    // ...
}

[kyyleofthemist]

thanks guys, i'll try these and let you know how it goes.

[kyyleofthemist]

alright that worked, but i'm having trouble with having the program read every number like its supposed to.

[hamsterman]

what does it read then?