On 02/08/2011 17:39, Jürgen Hestermann wrote:
In general I find the "with" statement very useful and have used and
do use it a lot. Though it must be used in well defined short code
blocks only. If you have very convoluted data structures with deeply
nested arrays and records and pointers to them then it is a benefit
not to be forced to write the same expression over and over again. And
it also saves the program from calculating array indices and other
references in these expressions multiple times so it speeds up the
code too. I.e., if you have an expression like this:
-----------------------------------------------------------------------
AusdehnungInMeter :=
(Qarray[QuaderNr]^.Teilung[R].Feldgrenzen[length(Qarray[QuaderNr]^.Teilung[R].Einteilungen)+1]
-
Qarray[QuaderNr]^.Teilung[R].Feldgrenzen[1]) *
EinheitAuswahl[Uebergabe^.Einheit.Koord[R]].Faktor;
-----------------------------------------------------------------------
it is much easier to read (and calculate) in a with statement:
-----------------------------------------------------------------------
with Uebergabe^, Qarray[QuaderNr]^.Teilung[R] do
AusdehnungInMeter := (Feldgrenzen[length(Einteilungen)+1] -
Feldgrenzen[1]) *
EinheitAuswahl[Einheit.Koord[R]].Faktor;
-----------------------------------------------------------------------
Why put Uebergabe^ in the with? It appears only once?
Assuming objects, better add helper methods
function TFooTeilung.GetLastFirstDiff;
begin
Result := Feldgrenzen[ length(Einteilungen)+1 ] - Feldgrenzen[1];
end
AusdehnungInMeter :=
Qarray[QuaderNr]^.Teilung[R]. GetLastFirstDiff
* EinheitAuswahl[Uebergabe^.Einheit.Koord[R]].Faktor;
You can also introduce
FeldgrenzenBackwards[x]
where 0 returns the last, 1 the one before last ....
If it may be other than last and first, give 2 params to
GetLastFirstDiff( ElemFromEndIdx, ElemFromStartIdx )
eg GetLastFirstDiff(0,0) for Last-First
Would further shorten this (assuming that Einteilungen and Feldgrenzen
are of the same length ?)
IMHO, that makes it much more readable.
you can even add an appropriately named method to the object returned by
"Qarray[QuaderNr]^" , if it is an object (or record with method)
AusdehnungInMeter :=
Qarray[QuaderNr]^. GetLastFirstDiffForTeilung(R)
* EinheitAuswahl[Uebergabe^.Einheit.Koord[R]].Faktor;
OR
AusdehnungInMeter :=
Qarray[QuaderNr]^. GetLastFirstDiffForTeilungFooBar(R, Uebergabe)
and do the multiplikation inside that (you got Uebergabe and R
Martin
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