Reading Assignment: All of Programming Ch4 Writing Code
Planning first is not only the best approach for novices, but also for skilled programmers. Having a clear plan of what the program should do at each step makes the debugging process significantly easier.
Step 1: Work an example yourself
The first step to devising an algorithm is to work an instance of the problem yourself. Often, a key part of working the problem yourself is drawing a picture of the problem and its solution. Drawing a clear and precise pictures allows you to visualize the state of the problem as you manipulate it. And it will help you with the next step, in which you write down precisely what you did on this instance of the problem.
An example of computation of overlapped rectangle is given. Hints are given below:
- Learning to put the obvious aside and think about what is going on is a key programming skill to learn, but takes some time.
- It is better to spend extra time in an earlier step of programming than getting stuck in a later step(if you do get stuck, you might want to go back to an earlier step and redo it with another instance of the problem).
Step 2: Write down what you just did
Now, you are ready to think about what it was exactly that you just did, and write down a step-by-step approach to solve one specific instance of the problem.
Step 3: Generalize your steps
This step is often the most important and most mistake prone.
Generalizing Values
Generalizing Repetitions
Generalizing Conditional Behavior
Generalization: An Iterative Process
Step 4: Test Your Algorithm
Here are some guidelines to help you devise a good set of test cases to use in Step 4:
- Try test cases that are qualitatively different from what you used to design your algorithm.
- Try to find corner cases–inputs where your algorithm behaves differently.
- Try to obtain statement coverage–that is between all of your test cases, each line in the algorithm should be executed at least once.
- Examine your algorithm and see if there are any apparent oddities in this behavior.
Step 5: Translation to Code
Composability
You do not have to do anything special to write a loop inside of another loop, nor to write a conditional statement inside of a loop–you can just put the pieces together and they work as expected.
The ability to put things together and have them work as expected is called composability and is important to building not only programs, but other complex systems.
Finishing Our Earlier Examples
A Complete Example
Writing the isPrime function.
Next Steps: Compiling, Running, Testing and Debugging
- Step 6: Testing your program
- Step 7: Debugging it