How do I check if an integer is assigned

[Thaddy]

Oh yeah, very smart to use extended, which is a reserved word, in your code.

Code: Pascal  [Select][+][-]

1. type
2.     person = class
3.     private
4.            x,y,vx,vy : integer;
5.            extended : boolean;
6.  

That's worse than trolling. That is clueless. And you do that on purpose?
(I am rather limited to water guns since I live in a grown up territory)

[deananorth]

Ah, didn't realise "Extended" was a reserved word.

My mistake.

I'll quickly change that.

Code: Pascal  [Select][+][-]

1. type
2.     person = class
3.     private
4.            x,y,vx,vy : integer;
5.            hasattr : boolean;
6.     public
7.            constructor create; overload;
8.            constructor create(args : array of integer); overload;
9.            procedure sayhi;
10.     end;
11.  

Aaaaaannnd that should be that.

I'm kinda new to pascal.

Also, out of curiosity. Why does "extended" highlight in Vim but not in Lazarus?

[rvk]

Oh yeah, very smart to use extended, which is a reserved word, in your code.

Uh, Thaddy, are you really sure extended is a reserved word ?????
https://www.freepascal.org/docs-html/ref/refse3.html

Extended words cannot be be redefined by the programmer and I'm sure extended can be redefined.

Also, extended isn't highlighted in the IDE, and all reserved words should be.

Extended is a type (like Integer and Double). So it is best not to use it anyway as a variable-name.

[deananorth]

Turns out Extended is a data type, and Lazarus doesn't seem to highlight data types.

From what I've read, it's a kind of floating point number that is a little longer (and thus more precise) than a double and is usually used on intel x86 processors.

Trying to use extended on other processors such as ARM tend to end up as a double with a different lick of paint.

Source: https://www.freepascal.org/docs-html/prog/progsu159.html

[totya]

I don't understand clearly what is the problem, but I play with it... :p

Code: Pascal  [Select][+][-]

1. unit mainform;
2.  
3. {$mode objfpc}{$H+}
4.  
5. interface
6.  
7. uses
8.   Classes, SysUtils, FileUtil, Forms, Controls, Graphics, Dialogs, StdCtrls,
9.   unit_clevervalue;
10.  
11. type
12.  
13.   { TForm1 }
14.  
15.   TForm1 = class(TForm)
16.     Button1: TButton;
17.     Memo1: TMemo;
18.     procedure Button1Click(Sender: TObject);
19.   private
20.     x: TCleverValue;
21.   public
22.     procedure ShowValue(const cv: TCleverValue);
23.  
24.   end;
25.  
26. var
27.   Form1: TForm1;
28.  
29. implementation
30.  
31. {$R *.lfm}
32.  
33. { TForm1 }
34.  
35. procedure TForm1.ShowValue(const cv: TCleverValue);
36. var
37.   s1, s2: string;
38. begin
39.   s1:=''; s2:='';
40.  
41.   if cv=nil
42.     then s2:= '(nil)'
43.     else s2:= '(not nil)';
44.  
45.   if cv<>nil then
46.     if cv.GotValue
47.       then s1:= '(got value)'
48.       else s1:= '(untouched)';
49.  
50.   if cv<> nil
51.     then Memo1.Lines.Add('x: '+s1+' , '+s2+' value: '+IntToStr(cv.Value))
52.     else Memo1.Lines.Add('x: '+s2);
53. end;
54.  
55. procedure TForm1.Button1Click(Sender: TObject);
56. begin
57.   Memo1.Clear;
58.  
59.   ShowValue(x);
60.  
61.   x:= nil;
62.   x:= TCleverValue.Create;
63.  
64.   try
65.     ShowValue(x);
66.       x.Value:= 10;
67.     ShowValue(x);
68.       x.Value:= 200;
69.     ShowValue(x);
70.       x.Value:= 0;
71.     ShowValue(x);
72.       x.Value:= 300;
73.     ShowValue(x);
74.   finally
75.     if Assigned(x) then FreeAndNil(x);
76.   end;
77.  
78.   ShowValue(x);
79. end;
80.  
81. end.
82.  

Code: Pascal  [Select][+][-]

1. unit unit_clevervalue;
2.  
3. {$mode objfpc}{$H+}
4.  
5. interface
6.  
7. uses
8.   Classes, SysUtils;
9.  
10. type
11.   TCleverValue = class
12.     public
13.       constructor Create;
14.  
15.     private
16.       FValue : integer;
17.     protected
18.       procedure SetValue (const _Value: integer);
19.     public
20.       property
21.         Value: integer read FValue write SetValue;
22.  
23.     private
24.       FGotValue: boolean;
25.     public
26.       property GotValue : boolean read FGotValue;
27.   end;
28.  
29.  
30. implementation
31.  
32. constructor TCleverValue.Create;
33. begin
34.   FValue:= 0;
35.   FGotValue:= false;
36. end;
37.  
38. procedure TCleverValue.SetValue (const _Value: integer);
39. begin
40.   FValue:= _Value;
41.   FGotValue:= true;
42. end;
43.  
44. end.
45.  

[rvk]

I don't understand clearly what is the problem, but I play with it... :p

There is no problem.
Try reading beyond the first few messages in this topic.

[totya]

I don't understand clearly what is the problem, but I play with it... :p

There is no problem.
Try reading beyond the first few messages in this topic.

Okay, but I don't see any important things... The result is similar, he use additional boolean variable as I. In my code this boolean show this variable clean or not, he code show override is executed or not.

[rvk]

Okay, but I don't see any important things... The result is similar, he use additional boolean variable as I. In my code this boolean show this variable clean or not, he code show override is executed or not.

Then you could just as easily have used a variant.
You can just check if varType(x) is varInteger and you know if it has been assigned an integer.

But you're correct. TCleverValue is one of the multiple possible ways to mark if a variable is assigned or not.