Re: Community Input for the Maintenance and Revision of the Ada Programming Language

["G.B." <bauhaus@notmyhomepage.invalid>]

On 02.10.17 12:06, reinert wrote:
> Not a big issue, but why does not this function:
>
>     if t1 < Clock and Clock < t2 then ...
>
> Should it?

The compiler should accept because the line means

     if "<" (clock, t1) and "<" (clock, t2) then ...

and "<" is defined for Time values.

But the order of evaluation is not determined when writing
the expression in the above way.
    First, "and" is different from "and then". This should
matter when calling Clock if real time is intrinsically sequential.
Second, consider reasons why in SPARK Ada you'll be asked
to always store the result of Clock into a variable (or
constant) by assignment and then use that variable.


>     if Clock in t1 .. t2 then         -- this dows *not* function


     14.     if Clock in t1 .. t2 then         -- this dows *not* function
                            |
         >>> scalar type required for range

This does not work because Time is not a scalar type, even though
time per se, if measured in seconds, say, can make one think it is
of a scalar type. But type Time is private, in Ada, an abstract
point in time, not a number of time units.