adder

Adder

From your fork of the repository, go to the lip/basics directory and create a new project with the following command:

dune init project adder

Executing the command will preserve the files bin/main.ml and lib/adder.ml in the folders adder/bin and adder/lib, respectively. Check that the directory test does not contain a file named adder.ml (if so, remove it), and ensure that the file test/dune is exactly as follows:

(library
 (name addertest)
 (inline_tests) 
 (preprocess (pps ppx_inline_test))
 (libraries adder))

Now, give a look at bin/main.ml. The main routine reads a line from the stdin. The expected format is a sequence of integers separated by spaces, like e.g.:

1 2 3

The program converts this line into a list of integers, and then prints their sum. The function that adds the elements of the list is partially specified in the file lib/adder.ml:

val addlist : int list -> int

The first task is to complete the implementation of the addlist function.

Testing and debugging

After you have completed the previous task, you can run the project with the command dune exec adder. This automatically builds the project, so you do not need to run dune build.

If the build gives no errors but the output is not the desired one, you can test the addlist function by running the following command from the adder directory:

dune utop lib

This command enters a REPL environment. To use it, first open the Adder library:

open Adder;;

At this point, you can test the functions you have defined in the lib/adder.ml file. In this case we only have one function, addlist:

addlist;;
- : int list -> int = <fun>

Debug your implementation in utop until it works correctly:

addlist [1;2;3];;
- : int = 6

Tip

Having to type open Adder every time you start utop can get quite annoying. This can be avoided by creating a file called .ocamlinit under adder/ containing the line:

open Adder.Main;;

Then run utop as usual. The Adder.Main module will be opened for you automatically!

Unit tests

Once you have completed the implementation, you can run some unit tests:

dune test

If you see an empty output, it means that your code has passed all the unit tests. Try to add new tests in the file test/addertest.ml.

Troubleshooting

1. Error: I cannot find the root of the current workspace/project.

Make sure you are running the commands dune build, dune test and the like from lip/basic/adder, the project's root folder.

2. I get an Error: Module "Addertest" is used in several stanzas after running dune build

Make sure the file dune under adder/test looks exactly like this:

(library
 (name addertest)
 (inline_tests) 
 (preprocess (pps ppx_inline_test))
 (libraries adder))

You may need to remove a few undesired lines that were added by dune init.

3. I get the following error after running dune build:

File "test/addertest.ml", line 3, characters 13-20:
3 | let%test _ = addlist [] = 0
                 ^^^^^^^
Error: Unbound value addlist

Remove adder.ml in adder/test. Make sure the structure of this folder looks exactly like this:

test
├── addertest.ml
└── dune