Constants in constant expressions

[BarrOff]

Hello

I just picked up Pascal/Lazarus after using Delphi more than 10 years ago.
Trying to run some samples, I stumbled across an error when using a constant in the declaration of another constant, see following mwe:

Code: Pascal  [Select][+][-]

1. Program Example;
2.  
3. Const
4.   x: Integer = 42;
5.   y: Integer = x;
6.  
7. Begin
8.   writeln('Hello');
9. End.

I get the following output when compiling with "fpc example.pas":

Code: Text  [Select][+][-]

1. Free Pascal Compiler version 3.2.2 [2021/07/09] for x86_64
2. Copyright (c) 1993-2021 by Florian Klaempfl and others
3. Target OS: Linux for x86-64
4. Compiling example.pas
5. example.pas(6,17) Error: Illegal expression
6. example.pas(11) Fatal: There were 1 errors compiling module, stopping
7. Fatal: Compilation aborted
8. Error: /usr/bin/ppcx64 returned an error exitcode

If I replace the x in y's definition with the literal value it compiles fine.

Now I have three questions:

1. Why does this error occur when using the constant but not when using a literal?
2. How can I fix this?
3. Is there maybe another (more idiomatic?) way to achieve the same result?

[TRon]

1. Why does this error occur when using the constant but not when using a literal?

Because the use of a typed constants (and not a real constant).

2. How can I fix this?

Use real constants instead of typed constants.

3. Is there maybe another (more idiomatic?) way to achieve the same result?

Code: Pascal  [Select][+][-]

1. Const
2.   x = Integer(42);
3.   y = integer(x);
4.  

?

[Thaddy]

Code: Pascal  [Select][+][-]

1. Const
2.   x = 42;
3.   y = x;

This resolves to integers anyway and does not take storage.

[440bx]

Now I have three questions:

1. Why does this error occur when using the constant but not when using a literal?
2. How can I fix this?
3. Is there maybe another (more idiomatic?) way to achieve the same result?

Answers:

1. Neither x nor y are _compiler_ constants, they are stored in memory therefore they are variables.  This is the case in both FPC and Delphi.

2. Make them compiler constants by removing the type, e.g, x = 42;  (note the removal of the integer type)

3. see 2. above.

For the record, Delphi would NOT have compiled that code either.

HTH.