Re: [Caml-list] Frustrated Beginner

[Michael Vanier <mvanier@cs.caltech.edu>]

To learn the functional style of programming I strongly recommend Abelson
and Sussman's Structure and Interpretation of Computer Programs.  Even
though it uses scheme, not ocaml, the functional style easily transfers
from one language to another.

Mike

> Cc: caml-list@inria.fr
> From: Tyler Eaves <tyler@ml1.net>
> Date: Tue, 23 Dec 2003 01:11:08 -0500
> 
> 
> 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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