A guide for how to attack an MP:
- Download mpXgrader.tar.gz and untar it (tar xzf
mpXgrader.tar.gz where X is the number
of the MP). This will create an mpXgrader
directory. Go into that directory.
- Carefully read the README file with MP-specific instructions.
- Copy the mpX-skeleton.ml file as
mpX.ml. To make sure you have all the
necessary pieces, start by executing make. This will create
the grader executable. Run the executable
(./grader). Examine the failing test cases for places where
errors produced by your code. At this point, everything should
compile, but the score will be 0.
- Read and understand the problem for the handout that you wish to
begin working on. (Usually, working from top to bottom makes most
sense.) There is a tests file in this directory. This is
an important file containing the an incomplete set of test cases;
you'll want to add more cases to test your code more thoroughly.
Reread the problem from the handout, examining any sample output
given. Open the tests file in the
mpXgrader directory. Find the test cases
given for that problem. Add your own test cases by following the
same pattern as of the existing test cases. Try to get a good
coverage of your function's behaviour. You should even try to have
enough cases to guarantee that you will catch any errors. (This is
not always possible, but a desirable goal.) And yes, test cases
should be written even before starting the implementation of your
function. This is a good software development practice.
- If necessary, reread the stament of the problem once more. Place
your code for the solution in mpX.ml,
replacing the stub found there for it. Implement your function.
Try to do this in a step-wise fashion. When you think you have a
solution (or enough of a part of one to compile and be worth
testing), save you work and execute make and the
./grader again. Examine the passing and failing test cases
again. Each failure is an instance where your code failed to give
the right output for the given input, and you will need to examine
your code to figure out why. When you are finished making a round
of corrections, run make, followed by ./grader
again. Continue until you find no more errors.
- When your code no longer generates any errors for the problem on
which you were working, return to steps 3) and 4) to proceed with
the next problem you wish to solve, until there are no more problems
to be solved.
| Interactive Debugging |
In addition to running "make" and "grader", you probably want to test your
code interactively at the top level:
- Enter the directory with your source file.
- Type ocaml at the command line.
- Type #load "mpXcommon.cmo";; at the OCaml prompt, where X is the number of the assignment (this loads in the common stuff that we give you by defualt).
- Type #use "mpX.ml";; at the OCaml prompt, where X is the number of the assignment. This loads in your code, and adds the functions you have defined to the identifiers recognized at top level.
- Type in commands followed by ';;' at the OCaml prompt to test your code interactively. Anything that you can do in a code file, you can do interactively. For example, you can define identifiers using 'let x = ...', etc...
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