Mail #9130

Back to main page of archive

Previous mail   Next mail   Unformatted/full headers
Overview  10 days   Subject   Date   Thread   Author  

From: Gale Paeper
Subject: Units and --uscd-pascal
Date: 30 Jul 2003, 23:05:21

Frank Heckenbach wrote:
> 
> Gale Paeper wrote:
> 
> > > Oh dear, I'm quite shocked. Why do people make up such strange
> > > things? They could easily have made two separate routines (say
> > > `ScanEQ' and `ScanNE' -- this might be what can be implemented
> > > reasonably in GPC, with different syntax (*)) -- it would have taken
> > > them just one more predefined identifier instead of a completely
> > > irregular new syntax rule ...
> >
> > I'm not sure where in the chain from Apple's UCSD Pascal to MPW Pascal
> > the change was made, but in MPW Pascal `ScanEQ' and `ScanNE' is provided
> > instead of Scan.
> 
> Even the same names that I'd just made up? :-)

Yep.  Although they're documented with a lower case spelling but that's
irrelevant for Pascal.
 
[snip]

> > How about:
> >
> > {$define Scan(A, B, C)
> >   repeat
> 
> Scan in UCSD Pascal is a function, so a compatibility macro must be
> usable as a function.

That B parameter is so demented that it causes mind rot. Completely
forgot about the function aspects.
 
> >     var ScanExpression : string(4) value (#B);
> >     if (Length(ScanExpression) = 4) and_then (index(ScanExpression,
> > '<>') = 1) then
> >       ScanNE((A),ScanExpression[4],(C))
> 
> BTW, would these parentheses actually be necessary in Pascal? Sure,
> it won't hurt to add them, but without the infamous comma operator
> of C, I think there could be no confusion here, anyway.

Probably not.  Just a C macro rule of thumb bleeding over to Pascal usage.
 
> >     else if (Length(ScanExpression) = 3) and_then (index(ScanExpression,
> > '=') = 1) then
> >       ScanEQ((A),ScanExpression[3],(C))
> >     else
> >       ParameterError;
> >   until true;
> 
> `repeat ... until True'? (Without trailing `;', BTW.) Perhaps you've
> read/written too many C macros of the kind `do ... while (0)'.
> 
> In Pascal, however, `begin ... end' would seem simpler (in a
> statement context), wouldn't it? (One of my favourite arguments why
> semicolon as a separator is better, BTW. :-)

Been reading too many C macros.
 
[snip]
> 
> Also, your suggestion would shift quite some work to runtime (string
> comparisons), and a parameter error wouldn't be detected until
> runtime. (I didn't check for it in my version, but it could be added
> and checked for at compile-time.)

I was thinking that the only way a macro hack would work is if the B
parameter was in a form where everything was compile-time constant
expressions and all but one of ScanEQ , ScanNE, or ParameterError would
get optimized away by the compiler.

In regards to ParameterError, that was more for completeness than
anything else.  At least to me, the only reason for this sort of macro
hack is to aid in porting old, presumably correct code so there
shouldn't be any errors to detect anyway (or at least one hopes so).

 
Adriaan van Os wrote:
> 
> The CH part can be an expression and it is quoted for char constants. I
> think it is (much) better to replace Scan by ScanEQ and ScanNE in the
> source code. 

I agree.  UCSD Scan is one of those things that is best left in the
graveyard of bad ideas.  

Gale Paeper
gpaeper@empirenet.com

Previous mail   Next mail   Unformatted/full headers
Overview  10 days   Subject   Date   Thread   Author  

In reply to

Back to main page of archive

Note: This page contains information that does not originate from the owner of this web site, but from the authors of the mails archived. The owner of this web site is not responsible for the content of such information. Any use of that infomation requires the consent of the respective author.

Where WWW addresses (URLs) in the mails archived are marked as hyperlinks, this is only for the comfort of the reader. The content of the web pages linked to like this does not necessarily reflect the opinion of the owner of this web site or of the authors of the mails archived. The owner of this web site is not responsible for the content of such web pages. Those pages are explicitly not to be considered as part of the content of this page, but merely as references.

This page was created by Crystal 0.999 (Linux 2.4.27/i686).