Re: language design tradeoffs

macrakis@osf.org (Stavros Macrakis) writes:
>>There are other possible conventions, as used in, e.g., Ada:


>>1) Use "end X" where X is the name of the opening delimiter, e.g. "end
>> loop;", "end record;" etc.


>>2) Use "end X" where X is the name of the named unit (e.g. function,
>> module, ...).


bromage@mullauna.cs.mu.OZ.AU (Andrew Bromage) writes:
>The problem here is that you end up with an amazingly verbose language
>like Pascal, which is a pain to type in.


Is a little verbosity a bad thing? I work with a language(Turing) that will
allow short forms so that
if a < b then
x := y
end if
    can become
[a<b:x:=y]
    the second is much harder to maintain when an 80,000 line program is
    completly written this way.


>My favourite solution comes from BASIC, where the statement terminator :
>is an _extension_ to the normal business of using EOL do terminate a
>statement. More modern versions of similar ideas can be found in languages
>like Turing.


Turing has no statment seperators/terminators.


>How do you allow the omission of the semicolon in languages like this at
>the end of a line? It's easy using a predictive parser because the end of
>the statement can be predicted. Does anyone have a "best way" of doing
>this with an LR parser?


There is no need for a language to require staement seperators or
terminators a little judicious design can get you around that problem.
Turing is an example of such a language.


Turing uses a PDA discription language called S/SL to help generate
various stages of compilation (scanning/syntax/semantic/code-generation).
S/SL claims to be equal in descriptive power to an LR(k) parser. At one
point in Turing's history a yacc grammer was generated to verify that the
language had no context sensitive features.
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