Basics for the assignments

How are we doing what we’re doing?

So nearly everyone has opened files in C++ or other languages before. Hooray! We’ll go ahead and take it one step further and read from stdinput that is, your program will take as a command line argument the name of a file.¹ If no argument is given, assume the file is test.txt.

For further reading, search Google, specifically for results from StackOverflow, and feel free to ask me if you need help. On the file IO portion, I’m fine if you use an LLM². However, the actual assigned content (e.g. finding the transitive closure of a relation using Warshall’s algorithm must be your own work, implementing the algorithms we learned.)

But wait, how do I read a filename from the command line? #

In C++: #

Instead of using

    int main(void) {
    ...
    }

You'll write your program using the following template:

    #include <string>
    #include <fstream>
    #include <iostream>
    using namespace std;
    int main(int argc, char* argv[]) {
        if (argc > 1) {     
            ifstream fin;
            fin.open(argv[1]);
        // ... do stuff with the file... 
            string aLineWeRead;
            getline(fin, aLineWeRead); 
        ...
      }
    }

In Python #

Here's a basic template you can use:

import sys

with open(sys.argv[1]) as f: 
   # do something with the file
   aLineWeRead = f.readline()
   ...
...

In Java #

If you're using standard java, the main static method will be:

class Closures {
...
    public static void main(String[] args) { 
       // do something with the file; note: the filename is args[0]. 
       ...
    } 
...
}

Writing to stdout #

All of the programs will output to stdout. I use this output data to compare against correctly computed values. You can do this via a number of mechanisms in your chosen Language. Here is one way in each of the above listed languages:

• In C++, it’s std::cout << "text to output"
• In Python, you can use print("text to output")
• In Java, it’s system.out.println("text to output")

I will be trimming out whitespace from your output, so you don’t need to worry about that.