Hi,
Leaving aside the reason why the MiSchi's solution doesn't work the main
question is still not answered :)
If you have integer dynamic array "MyArray" is there a way for the
following statement to compile and work correctly:
MyArray := 5;
Thanks,
Gennady
On 11/3/2018 4:14 PM, Ben Grasset wrote:
On Sat, Nov 3, 2018 at 8:01 AM Schindler Karl-Michael
<karl-michael.schind...@web.de <mailto:karl-michael.schind...@web.de>>
wrote:
Hi
I would like to use a simple assignment operator for arrays, with
which all elements of an array are assigned to the same value,
similar to an extended initialize, not to zero but to a value of
choice. A simple example for an integer array would be:
myArray := 5;
With arrays with defined bounds, it works, but i was not able to
do it with a dynamic array. My test case is this:
program arrayAssign;
type
TmyArray = array of integer;
var
myArray: TmyArray;
index: integer;
operator := (const number: integer) theResult: TmyArray;
var
i: integer;
begin
for i := low(theResult) to high(theResult) do
theResult[i] := number;
end;
begin
setlength(myArray, 10);
writeln ('myArray: ', low(myArray), ', ', high(myArray));
myArray := 5;
writeln ('myArray: ', low(myArray), ', ', high(myArray));
for index := low(myArray) to high(myArray) do
writeln (index, ': ', myArray[index]);
end.
The output is:
myArray: 0, 9
myArray: 0, -1
The problem is that in the declaration of the operator, the
functions low and high seem to return the values of the type
TmyArray, i.e. 0 and -1 and not the values of the variable of the
assignment statement, i.e. myArray and the assignment nullifies
the previous setlength. Is there any way around this and obtain
the actual values of myArray?
Michael, aka MiSchi.
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There's two issues:
1) The result of the operator is always a new, unique array (as in
it's unrelated to the myArray variable)
2) Your operator doesn't initialize the result with a length, so it's
just iterating over nothing.
Here's an example of the correct way to write the operator and use it:
program ArrayOverloads;
{$mode ObjFPC}
type TIntArray = array of Integer;
operator := (const I: Integer): TIntArray; inline;
var V: Integer;
begin
SetLength(Result, I);
for V := 0 to Pred(I) do Result[V] := V;
end;
var
I: Integer;
IA: TIntArray;
begin
IA := 25;
for I in IA do Write(I, ' ');
WriteLn;
for I := High(IA) downto 0 do Write(I, ' ');
WriteLn;
for I := Low(IA) to High(IA) do Write(I, ' ');
WriteLn;
I := 0;
while I < Pred(High(IA)) do begin
Inc(I, 2);
Write(I, ' ');
end;
end.
Output:
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
2 4 6 8 10 12 14 16 18 20 22 24
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