Does delphi have some "fast" operators ? (+=, -=, ...)

Question

Hello,

Very simple question but I couldn't find an answer on google

In delphi, is there a way to shorten this kind of code:

MyVar := MyVar + X;

Like in C++ I would do MyVar += X;. Given how trivial and useful it is there must be way, but I can't find any option for that anywhere ...

Thanks for any help

Answer 1

You could use the Inc command like this:

Inc(MyVar, X);

Answer 2

Inc(MyVar, X);

won't get any shorter, I fear.

Answer 3

'Do and Assign' operators like += and -= aren't part of the Delphi specification language - you'll need to do your incrementing another, likely longer, way.

Answer 4

No, you don't. But you can use the

procedure Inc(var X [ ; N: longint ] );
Inc(avar)
Inc(avar, 10)

to increment a variable by N, or

procedure Dec(var X [ ; N: longint ] );
Dec(avar);
Dec(avar, 10);

to decremente a variable by N.

Answer 5

Are you looking for "fast" or short operators? Inc and Dec, as suggested, are the closest in function and length to += and -=, but they are also faster under some circumstances. If you have range checking turned on then they are faster then calling x := x + 1;

Here is the disassembly with range checking turned on, where all variables are a bytes (max value of $ff) for Inc(MyVar, x)

// Inc(MyVar, x);
  add bl, x

And here it is for x := x + 1;

// x := x + 1;
  movzx eax,bl
  movzx edx, x
  add eax,edx
  cmp eax,$000000ff
  jbe success
  call @BoundErr
success:
  mov ebx,eax

You can see the difference, even if there is not a range check failure.

However if you turn on Overflow checking, Inc is still subject to that overhead.

Answer 6

In delphi, is there a way to shorten this kind of code:

What are you trying to shorten? x = x + 1 and x += 1 generate identical code in languages that support them (for standard types). Since Delphi doesn't have operator overloading, x := x + 1 is an integer or a float operation. The code syntax is just that: syntax. The one is no "faster" than the other.