Introduction to Computational Linguistics

2. Practical Remarks Concerning OCaML 3
It then starts the interactive session by giving you a command prompt: #. It is then
waiting for you to type in a command. For example
(2) # 4+5;;
It will execute this and return to you as follows:
(3)
- : int = 9
#
So, it gives you an answer (the number 9), which is always accompanied by some
indication of the type of the object. (Often you find that you get only the type information,
see below for reasons.) After that, OCaML gives you back the prompt.
Notice that your line must end in ;; (after which you have to hit < return >, of
course). This will cause OCaML to parse it as a complete expression and it will
try to execute it. Here is another example.
(4) # let a = ’q’;;
In this case, the command says that it should assign the character q to the object
with name a. Here is what OCaML answers:
(5) val a : char = ’q’
Then it will give you the prompt again. Notice that OCaML answers without
using the prompt, #. This is how you can tell your input from OCaMLs answers.
Suppose you type
(6) # Char.code ’a’;;
Then OCaML will answer
(7) - : int = 113
Then it will give you the prompt again. At a certain point this way of using
OCaML turns out to be tedious. For even though one can type in entire programs
this way, there is no way to correct mistakes once a line has been entered. Therefore,
the following is advisable to do.
First, you need to use an editor (I recommend to use either emacs or vim;
vim runs on all platforms, and it can be downloaded and installed with no charge