Can one initialize multiple variables of some type in one line?

Question

I have been trying to write as less code as possible. So, I use:

MyBoolean := Memo1.Text <> '';

instead of

if Memo1.Text = '' then
  MyBoolean := true
else
  MyBoolean := false;

Declare and initialize

var
  myGlobal: integer = 99;

to declare and initialize global variable. I would like to do the same for local variables, but seems it is not possible, so, I wonder if there is a way to initialize multiple variables of some type in one line, like in C

int x, y, z;
x=y=z=0;

Thank you.

Answer 1

You can only initialize a single local variable per statement.

Answer 2

In C assignment is an expression (returns a value).

In Pascal assignment is a statement (does not return a value).

The difference has some interesting consequences. For example in C both

while (x=0)

and

while (x==0)

are syntactically valid constructions (it is the source of innumerable errors) while in Pascal

while (x:=0)

is syntactically invalid because x:=0 is a statement.

Answer 3

Of course it would be possible to write a function

function AssignInteger(var _AssignTo: integer; _Value: integer): integer;
begin
  Result := _Value;
  _AssignTo := _Value;
end;

and use it like this:

var
  i, j, k: integer;
begin
  i := AssignInteger(j, AssignInteger(k, 5));

But that's not quite what you want, saying you want to write as short as possible code.

I'm pointing this out nonetheless just in case.

Answer 4

As dummzeuch says, you could write your own routine. However, I would prefer one with a signature something like: procedure AssignIntegers(AValue, ATargetArray);. And ideally call the routine with: AssignInteger(99, [X, Y, Z]);.

Unfortunately the ideal option does not work, but the following procedure is close enough and should suffice. It works by taking pointers to the integers that need to be assigned.

procedure AssignIntegers(AValue: Integer; const ATargets: array of PInteger);
var
  I: Integer;
begin
  for I := Low(ATargets) to High(ATargets) do
    ATargets[I]^ := AValue;
end;

The following DUnit test case demonstrates that it works. You can even keep an array of these integer pointers handy to reassign at any time.

type
  TArrayPInteger = array of PInteger;
procedure TDelphiTests.TestAssignIntegers;
var
  X,Y,Z: Integer;
  LGroup: TArrayPInteger;
begin
  AssignIntegers(1, [@X, @Y, @Z]); { Pass open arrray using addresses of integers to initialise }
  CheckEquals(1, X);
  CheckEquals(1, Y);
  CheckEquals(1, Z);

  LGroup := TArrayPInteger.Create(@X, @Y); { Handy technique to initialise dynamic arrays }
  AssignIntegers(2, LGroup);
  CheckEquals(2, X);
  CheckEquals(2, Y);
  CheckEquals(1, Z); { Not part of group }
end;

WARNING

The only real drawback is that you lose type-checking. The compiler won't prevent you from passing the address of non-integer types. This can lead to corrupting other structures' data or access violations.