[fpc-pascal] Writeable typed constants - what's the point?

Jonas Maebe jonas.maebe at elis.ugent.be
Thu Jun 18 10:56:26 CEST 2009

On 18 Jun 2009, at 08:51, Vincent Snijders wrote:

> Graeme Geldenhuys schreef:
>> Hi,
>> Recently I learned that you can have writeable typed constants. That
>> sounds rather like an oxymoron to my. Writeable constants make no  
>> sense,
>> is that then simply a variable? What is the use of a writeable typed
>> constant?
> Backwards compatibility with turbo pascal, which lacked initialized  
> variables and writable constants were the alternative.

Writable constants behave completely different from initialised  
variables inside procedures/functions: writable constants are  
initialised once (at program startup) and keep their value across  
invocations, while initialised variables are re-initialised every time  
the procedure/function scope is entered.

I.e., local writable constants are basically global initialised  
variables that are only visible inside a local scope.


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