[SOLVED] Assign existing constants to new constants...

[GypsyPrince]

Does Lazarus/ObjectPascal allow for assigning an existing constant to a new constant as shown here?

Code: Pascal  [Select][+][-]

1. m_HLP_ENG_CNCL : String = 'Procedure Execution';
2. m_HLP_ENG_FAIL : String = m_HLP_ENG_CNCL;

When I do this I get the error "Illegal expression".  Is this allowed? Or, might I just have my syntax incorrect?

[eljo]

try removing the : string definition from your constants and see if that helps.

[GypsyPrince]

@eljo

try removing the : string definition from your constants and see if that helps.

Already tried. Same error.

[eljo]

@eljo

try removing the : string definition from your constants and see if that helps.

Already tried. Same error.

the folowing is a simple program just created and executed in my windows 7 installation.

Code: Pascal  [Select][+][-]

1. program Project1;
2.  
3. const
4.   m_HLP_ENG_CNCL = 'Procedure Execution';
5.   m_HLP_ENG_FAIL = m_HLP_ENG_CNCL+'. Ends here';
6.  
7. begin
8.   writeln(m_HLP_ENG_CNCL);
9.   WriteLn(m_HLP_ENG_FAIL);
10. end.
11.  
12.  

No problems reported everything prints correctly in the console window.

[GypsyPrince]

I had to remove the type definition from both the new constants and the existing constants from which their value is assigned. It works now.  I wonder if it's a design flaw in Free Pascal or if the developers intended it that way...

[eljo]

as far as I remember its by design, something about different types of constants, never cared enough to remember it.

[GypsyPrince]

Oh yes, I forgot. Constants are mutable by default in Free Pascal.

[PascalDragon]

I had to remove the type definition from both the new constants and the existing constants from which their value is assigned. It works now.  I wonder if it's a design flaw in Free Pascal or if the developers intended it that way...

Constant and variable initializers can only use untyped constants and some internal functions (e.g. High, Ln, etc.).

[Thaddy]

And untyped constant is immutable. (as well as any typed constant declared in {$J-} state, I might add )

[GypsyPrince]

@PascalDragon and @Thaddy

And untyped constant is immutable. (as well as any typed constant declared in {$J-} state, I might add )

Constant and variable initializers can only use untyped constants and some internal functions (e.g. High, Ln, etc.).

These two points were proving to be an annoyance for me for a brief time because I generally prefer strongly typed data fields. However, after tinkering a bit more, I am beginning to feel a little more at ease with untyped fields.

[PascalDragon]

These two points were proving to be an annoyance for me for a brief time because I generally prefer strongly typed data fields. However, after tinkering a bit more, I am beginning to feel a little more at ease with untyped fields.

You can enforce a specific type using a typecast:

Code: Pascal  [Select][+][-]

1. const
2.   MyString = UnicodeString('Hello World');
3.   MyDWord = DWord(42);

And if you don't need to initialize another constant with it you can just as well use typed constants (and disable writeable constants).