[fpc-devel] [Suggestion] Enumeration range-check intrinsic

[Michael Van Canneyt]

On Fri, 5 Jul 2019, Martok wrote:

> Am 05.07.2019 um 02:52 schrieb Michael Van Canneyt:
>
>> With this sentence you forbid storing or communicating enumerated values in any way: 
>> file, database, over network. It can be used only in a computer program and never
>> leave the context of the running program under any form. Because as soon as
>> it is somehow communicated, there is a chance it becomes invalid in return
>> communication.
>
> This is the conclusion from Jonas' arguments, which he explicitly confirmed when
> we had the discussion two+ years ago.
>
> You're also missing another important type of 'communication': calling non-FPC
> APIs or even just FPC libraries of possibly different version (see: Run-Time
> Packages!)

APIs falls under 'communicating'. Database is an API. Library is an API,
REST is an API: you communicate the value to a system not under your
control.

> Anything that even looks like a subrange cannot be used for these interfaces.

Yes, if you adhere to a strict view.

But IMO such a strict stance is untenable: you cannot ensure correct values 
in all cases even within the confines of the language (as demonstrated before).

So, in my book, an intrinsic to check for a correct value in the places where an 
invalid value can enter the system is a welcome language feature.

Put another way:
If the programmer is responsible (correctly so) for ensuring correct values, 
then I think the language must give him the tools to fulfill his 
responsability in a convenient manner. Hence the need for an intrinsic.

Michael.