Re: Empty String confusion; Positive and Natural

[ldries46 <bertus.dries@planet.nl>]

Op 29-11-2021 om 18:34 schreef Kevin Chadwick:
> I suspect that I am doing something outside of Ada norms.
>
> Are empty strings avoided in Ada?
>
> I have a function to create a record containing strings amongst other things like a subtyped integer, simply to group the outputs neatly of another function.
>
> If something goes wrong and I run the create function with "" then the strings length is zero. Why is a string type Positive and not Natural, because empty strings are in fact useless?
>
> I guess I shall consider re-engineering my functions, rather than add checks, but all thoughts are welcome.
 From your description, I suspect that you are using different 
declarations for the strings you use for instance while " " in fact is a 
string(1.1) you try to put this in a string(1 .. 5).
To avoid this kind of problems I generally use the package 
Ada.Strings.Unbounded where have possibilities to operate strings 
without caring for the length. Changing between strings and unbounded 
strings is possible with functions in the package.
I would then advice you to create an variable at a position where it is 
reachable from all packages where you use it:
Empty_String : Unbounded_String := To_Unbounded_String("");