Re: [Caml-list] Frustrated Beginner

[Tyler Eaves <tyler@ml1.net>]

On Dec 23, 2003, at 12:34 AM, Matt Gushee wrote:
>
>> So why is O'Caml giving me so much trouble?
>
> Do you have any previous experience with functional programming (FP), 
> or
> have you studied FP in school? If not, then you're learning both a new
> syntax and a very different programming paradigm at once, so you should
> expect a steep learning curve. But I think if you stick with it, after 
> a
> while it will all start to make sense, and you'll be glad you made the
> effort.

Not much, a (very) little Lisp.  Not really enough to 'get it'.
>
>> I've been trying to pick it up for about a week now, read various
>> online tutorials.
>

>  http://www.merjis.com/richj/computers/ocaml/tutorial/
This is the one I've gotten the most out of.

>> My biggest source of problems seems to be the syntax. I'm totally
>> confused as far as ; vs ;; vs nothing, ...
>
> Yes, that is a bit tricky. You've undoubtedly read explanations of the
> semicolons, but sometimes it helps if you get the same information 
> again
> in slightly different terms, so let me try:
>
>   * A double semicolon ends a "sentence"--that is, it terminates a
>     top-level construct such as a function definition--but not nested
>     function definitions, because they're not "sentences," they're
>     "phrases".
>
>     You can omit ;; in most cases, but I would suggest at first using
>     it everywhere it is allowed. When you omit the ;; and there is a
>     syntax error in your code, the compiler often goes many lines past
>     the real trouble spot before it detects an error, so using ;;
>     everywhere can narrow down your search.
>
>   * The single semicolon is perhaps a bit harder to understand, but I
>     think it helps to keep in mind that OCaml is basically a functional
>     language, yet it also supports imperative programming. Being
>     functional means that there are no statements per se. It's all 
> about
>     evaluating expressions, and *every* expression returns a value.
>     However, there are expressions that are functionally equivalent to
>     statements. In order to conform to the functional model, they have
>     to return a value, but there is no useful value to return. So they
>     return the unit value, '()'.

Okay, that helps.

>     Basically, whenever you are programming imperatively--when you have
>     one of these pseudo-statements that return (), and when it this
>     imperative phrase is not the final result of a function, you need 
> to
>     separate it from the following phrase with a single semicolon. A
>     simple example:
>
>       match foo with
>       | None -> print_endline "Nothing"; ""
>       | Some x -> print_endline x; x

If I understand the match syntax correctly, in this case, x takes the 
value of foo?
>     This expression returns a string, but before returning, you want to
>     print a message. Printing functions, of course, return ().
>
> Hope this helps a bit. Best of luck to you

It does, quite a bit. Thanks to everyone else too, I've already gotten 
something like 11 replies in an hour and a half :)

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