Path: news.cs.au.dk!not-for-mail
From: Flemming Gram Christensen <gram@mjolner.dk>
Newsgroups: comp.lang.beta
Subject: Re: More newbie questions ...
Date: 30 May 2000 15:49:12 +0200
Organization: University of Aarhus, Department of Computer Science (DAIMI)
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Atle <trollet@skynet.be> writes:

> I have worked my way through some initial documentation, and only a few loose ends remain. 
> Hopefully, they should just require (Y/N) answers or one-liners. 
> Unfortunately, the saying goes: One idiot can ask more than ten wise men can answer :-)
> This why I might be asking the wrong question, and in that case, the answer may not be so simple after all ...
> 
> 1. Are compiler directives standardized across implmentations (Y/N)?

Most are. Which do you have in mind?

> 
> 2. Why are control structures called 'imperatives'? Can the difference be described with a 'one-liner', if not, I will be happy with
> just the name of a document outlining the philosophy behind the Beta control structures ('imperatives').

Imperatives are similar to statements in Pascal or C. They do not generate a result value.
This is opposed to evaluations.
The imperatives are: ( found in beta/grammars/beta/beta-meta.gram, the grammar 
   (please note the html version i beta/doc/grammars/beta) )
    <Imp> ::| <LabelledImp>
          | <ForImp>
          | <SimpleIfImp> 
          | <GeneralIfImp> 
          | <LeaveImp>
          | <RestartImp>
          | <InnerImp>
          | <SuspendImp>
          | <Evaluation>;


> 
> 3. Are loops part of the language, or are they meant to be specialized from a general case (Y/N)?
> 

Both. You can do a loop like:

(for 10 repeat
   "do something ten times" 
for);

or

(for i:12 repeat
   "do something parametrized by 'i' 12 times"
   "eg. i->putint;"
for);

or using a combination of a labelled imperative and restart/leave:

(# i:@integer;
do 0->i;    (* assign 0 (zero) to i *)
   loop:
    (if i < 8 then
        i->putint; ' is less than 8'->putline;
	i+1 -> i;        (* assign i+1 to i *)
	restart loop;    (* begin from if again *)
    if);
#);

etc.	

Another example is using the INNER construct. Eg. a list as found in beta/containers/list.bet
can be scanned using:

(# l:@list(# element::IntegerObject #);  (* declare list of integerObjects *)
do list.scan
   (# do current.value->putint;
   #);
#)



> With these things settled, I can start on my own hello.bet, and hopefully understand what I am doing along the way.
> 
> Is there a Beta User Group (sorry, I had to capitalize :-) where I can meet other newbies, people who have just typed in their first
> 'hello' program and want to program that killer app for the next millennium?
> A place with
> Best wishes Atle

You are welcome in this newsgroup. Ask away.

Flemming