To good optimization?

[Setharian]

It's still passed by value. You'd have to explicitly pass the integers as pointers by using "var". Then the "X := X + 10;" line would modify the source variable. Otherwise just the local copy of the variable is modified.

[Brainer]

It's still passed by value. You'd have to explicitly pass the integers as pointers by using "var". Then the "X := X + 10;" line would modify the source variable. Otherwise just the local copy of the variable is modified.

He's right. Compare these:
[pascal]
function MyPoint(X, Y: Integer): TMyPoint;
begin
X := X + 10;
Result.X := X;
Result.Y := Y;
end;

var
X, Y: Integer;
begin
X := 10;
Y := 20;
MyPoint(X, Y);
writeln(X);
readln;
end.
[/pascal]
[pascal]
function MyPoint(var X, Y: Integer): TMyPoint;
begin
X := X + 10;
Result.X := X;
Result.Y := Y;
end;

var
X, Y: Integer;
begin
X := 10;
Y := 20;
MyPoint(X, Y);
writeln(X);
readln;
end.
[/pascal]

In the first case, X after passing to MyPoint still equals 10. But in the latter, X is passed as a reference, thus it equals 20.

You can also use Assembler to boost up your program:
[pascal]
function MyPoint(X, Y: Integer): TMyPoint;
// EAX contains address of X
// EDX contains address of Y
// ECX contains the result
asm
mov [ECX], EAX
mov [ECX+4], EDX
end;
[/pascal]
But I doubt you'll gain any speed using this.

[arthurprs]

Const is for string, record and array parameters.

For anything with more than 4bytes in size

[cronodragon]

Const is for string, record and array parameters.

For anything with more than 4bytes in size

Hmm, a method type (procedure of object) has 8 bytes and I haven't seen any tip about passing it with Const. What the Delphi Help says is that const should be used with structure types.

[chronozphere]

Okay... thanx for the info... realy usefull

[arthurprs]

Const is for string, record and array parameters.

For anything with more than 4bytes in size

Hmm, a method type (procedure of object) has 8 bytes and I haven't seen any tip about passing it with Const. What the Delphi Help says is that const should be used with structure types.

Maybe its an "exeption" (not sure about this word)

[JSoftware]

What const does is simply declare it as a constant in the function. The function can thus not alter it on syntax level, and the compiler then knows that all variables can be passed by reference. This is only a good thing if the parameter is very big, like a string or a big record

With simple types you don't need it