Re: TeamB, Borland, admit obvious

From: Barry Kelly (barry_j_kelly_at_hotmail.com)
Date: 03/09/04 

Date: Tue, 09 Mar 2004 20:55:58 +0000

On Fri, 5 Mar 2004 13:10:56 +0100, "Hrvoje Brozovic" <a.b@c.de> wrote:

> Using the plus (+) operator has the same effect on two
> strings as using the Concat function:
> S := 'ABC' + 'DEF';
>
> Tip: The plus operator is faster than Concat.
>
> MY NOTE: Borland encourages developers to use it.

> s1 := s2 + s3 calls LStrCat3
> s1 := s1 + s2 calls LStrCat
>
> MY NOTE: Obviously s1 += s2 is treated as special case by Borland.

However, LStrCat cannot know how long the final string is going to be.

> MY NOTE: Borland always tries to resize in place,

Again, this *might* work *once*.

> When performing repeated concatenations of the type:
> For I = 1 To N
> Dest = Dest & Source
> Next N
>
> the length of time increases proportionally to N-squared.

This is true in Delphi and VB and in any other language compiler which
cannot fortell the future. I recommend using a TStringList or
something similar to build very long chains of concatenations.

> Steps 2 and 6 are very expensive and basically ...

A constant time increase, irrelevant as it will be dominated by the
n^2 function observed earlier.

> MY NOTE: to achieve performance in the same order of magnitude (but still
> much slower) as Delphi,
> Microsoft has nothing to offer Visual Basic developers other than hack.

This is incorrect. The Delphi native code is only slightly better than
VB, and only by a constant factor.

> If you going to use StringBuilder, it cant pass as
> minor change in anybody's book.

I already used TStringList as a StringBuilder, so I personally don't
see the problem. 

-- 
Barry Kelly
If you think the problem is bad now, just wait until we've solved it.
  -- Arthur Kasspe

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