Modifying string length?_(re)

Mon, 28 Apr 1997 21:05:12 +0200 (MET DST)

According to Frank Heckenbach:
>
> Well, the problem is, I said "efficiently".
> I don't assume, gpc would optimize statements like
>  s:=s+'a'
> where s is a (possibly quite long) string, so I'd have O(n) where actually
> O(1) is possible.

I would say:  GPC *does* optimize this.  Just type `gpc -O -S foo.pas'
and look at `foo.s' ...

> E.g. the examples from the documentation about converting
> CStrings to Pascal strings append char by char in a loop -- O(n^2) instead
> of O(n). I don't think that should be left as it is.

You mean the routines in the FAQ?  I think they are O(n) because
"S:= S + Src^" is inlined and optimized.  But of course, feel free
to improve those routines and send the result to Jan-Jaap ... ;-)

> I'd have to do it like this if there's no other way...
> But shouldn't it be possible to access the fields of the "string record" in
> a direct way? Perhaps in the course of the schema project?

It would not be too difficult to make "MyStr.length" and "MyStr.String" 
accessible "record fields" of strings.  Would it be desireable?  I am
not sure how this fits into the standard ...

Another thing *is* planned:  A new data type `ShortString' (or
`ShortStr'?)  which will be the UCSD/Borland version of Strings.  In many
contexts, they are better than Extended Pascal string schemata because
they have only 1 byte overhead instead of 8.  (But this will be a lot
of work.  Anybody interested to help here???)

> (Are you planning
> to make strings regular schema types then -- regular except for the extended
> syntax that allows s[n]?)

No.  They are exceptions in yet another way because they have the
implicit read-only "length" field.

Greetings,

    Peter

  Dipl.-Phys. Peter Gerwinski, Essen, Germany, free physicist and programmer
peter.gerwinski@uni-essen.de - http://home.pages.de/~peter.gerwinski/ [970201]
 maintainer GNU Pascal [970420] - http://home.pages.de/~gnu-pascal/ [970125]

Peter Gerwinski (peter@agnes.dida.physik.uni-essen.de)