Delphi array initialization

Question

I currently have this, and it sucks:

type TpointArray = array [0..3] of Tpoint;

class function rotationTable.offsets(pType, rotState, dir: integer): TpointA         


        

Answer 1

You cannot because you cannot express in the code body a point in the way in which you can express it in the const section.

However you can do some tricks in order to have your life easier, especially if you have a reasonable number of points.

You can implement a simple procedure like this (code not tested):

procedure BlendDimensions(aXArray, aYArray: TIntegerDynArray; var aResult: TPointArray);
var
  nCount: integer;
  i: integer;

begin
  nCount:=High(aXArray);
  if nCount <> High(aYArray) then 
    Exception.Create('The two dimension arrays must have the same number of elements!');

  SetLength(aResult, nCount);
  for i:=0 to nCount do
  begin
    aResult[i].X:=aXArray[i]; //simple copy
    aResult[i].y:=aYArray[i];
  end;
end;

...where TIntegerDynArray is the RTL's dynamic array of integers. (In fact it will work with any dynamic array). Also, TPointArray in the above example is also dynamic.

So, in order to do your job, you can do like this:

procedure Foo;
var
  myXCoords, myYCoords: TIntegerDynArray; //temp arrays
  myPoints: TPointArray; //this is the real thing

begin
  myXCoords:=TIntegerDynArray.Create( 1, 2, 3, 4, 5, 6, 7, 8, 9,10);
  myYCoords:=TIntegerDynArray.Create(21,32,34,44,55,66,65,77,88,92); //...for example 
  BlendDimensions(myXCoords, myYCoords, myPoints); //build the real thing
 //use it...
end;

Things to note:

• You see clearly which are your points
• You can be very productive in this way
• You can use BlendDimensions also on other things not only on this one
• You can easily expand BlendDimensions for 3 (or more) dimensions
• ...but beware because a copy is involved. :-) With today PCs, the weakpoint will be, by far, your hand. :-) You will get tired to type much more quickly till the copy time will be even noticed.

HTH