CSCI 261 - Programming Concepts (C++)

This lab is due by November 02, 2016 08:00am.

The focus on this assignment is on one main concept: how to write data to an "output file stream" or ofstream object.

In class today, we learned about how data can be written to files. Remember that whenever you work with a file stream as output, we call them ofstream objects.

There will always be four things you will do whenever working with an ofstream. Open the file, check for error, write some data, and close the file. The typical pattern for this is as follows:

Remember, once you have an ofstream object (like myCatsAges shown above) you use it in a manner similar to using cout.

Remember Lab06B where we created a simple Turtle Graphics program that printed out screen coordinates to our terminal? As an intermediate step towards Assignment 09, we are going to save our Turtle's location to an external file in addition to printing them to the terminal. You will probably want to use your solution to Lab06B as the starting part for this lab.

As before, first ask the user for the resolution of our circle appoximation. Print out the theta and distance that will be used. Now ask the user to enter a string for the filename that we want to save our points to. We now need to open an output file stream that will save data to the corresponding filename.

Before our program printed the coordinates to the terminal, now we want to print the coordinates to an external file. The file should have the following format;

# of points
Point1X Point1Y
Point2X Point2Y
Point3X Point3Y
etc...

That is, the first line should be the number of points we will print. Then each following line will be the X and Y location of each point, separated by a space.

Since we were using a recursive function previously to generate and print our points, we will want to pass our output file stream as an argument to the function. This is simple to do as it is just another variable. One thing to note, file streams may ONLY be passed by REFERENCE. As an example, the function below may be helpful (you might want to modify it, create different versions that accept different parameter types, etc.).

void PrintToFile( ofstream &out, const string txt ) {
    out << txt;
}

int main() {
    ofstream outFile;  // open outFile properly, etc.
    
    PrintToFile( outFile, "Hello World!" );
    
    return 0;
}

A sample program output is below:

Enter the resolution to approximate the circle to: 6
Theta = 1.047
Dist = 1.000

Enter a filename to save the points to: circle_6.txt
Saving points to file "circle_6.txt"...
...writing number of points 6 to file...
...writing point (1.500, 0.866) to file...
...writing point (1.000, 1.732) to file...
...writing point (0.000, 1.732) to file...
...writing point (-0.500, 0.866) to file...
...writing point (0.000, 0.000) to file...
...writing point (1.000, 0.000) to file...
...finished writing points! 

Our file should then have the following contents (based on the program above):

6
1.500 0.866
1.000 1.732
0.000 1.732
-0.500 0.866
0.000 0.000
1.000 0.000

This file will now serve as the input to Assignment 09.

You will submit your solution to this lab with the rest of Week09. Detailed instructions for doing this are posted in Assignment 09.

This lab is due by November 02, 2016 08:00am.