typed constants -v- true constants 1

[mmaxwell]

I am new to Delphi.

The following should work -

procedure TForm1.Button1Click(Sender: TObject);
const a: Integer=0;
begin
a:=7;
end;

I get error "Left side cannot be assigned to"

I would expect this if I used const a:=12; but not as above.

I would appreciate some guidance.

 

[Griffyn]

Delphi is right Constants cannot be assigned to aside from an initial declaration.

The difference between typed and non-typed constants is simply that Delphi will implicitly type a constant if you don't specify one. Consider the following:

procedure UseNumber(AInteger: Int64);
begin
...
end;

const
xxHelp = 0;
begin
UseNumber(xxHelp);
end.

In this example it will cause a compiler error, because xxHelp has been implicitly declared as an Integer, and therefore doesn't match the type of the UserNumber procedure. However, changing the const declaration to:

const
xxHelp : Int64 = 0;

will allow the program to compile.