Re: ADA.CALENDAR and midnight

[Brian May <bam@snoopy.apana.org.au>]

>>>>> "Nick" == Nick Roberts <nick.roberts@acm.org> writes:

    Nick> If Time_Of is called with a seconds value of 86_400.0, the value
    Nick> returned is equal to the value of Time_Of for the next day with a
    Nick> seconds value of 0.0. The value returned by the function Seconds or
    Nick> through the Seconds parameter of the procedure Split is always less
    Nick> than 86_400.0.

    Nick> So I would say that an implementation which returns 86_400.0 is
    Nick> faulty.

Hmmm.. Have to double check.

I have the following function (spot the bug!), for displaying times in
hh:mm:ss format.

>-------function To_String(The_Time : in Time) return String is
>------->-------Duration : Integer;
>------->-------H : Integer range 1..24;
>------->-------M : Integer range 0..60;
>------->-------S : Integer range 0..60;
>-------begin
>------->-------Duration := Integer(Seconds(The_Time));

>------->-------S := Duration mod 60;
>------->-------Duration := (Duration-S)/60;

>------->-------M := Duration mod 60;
>------->-------Duration := (Duration-M)/60;

>------->-------H := Duration;
>------->-------
>------->-------return Strip(Integer'Image(H))&":"
>------->------->-------&Strip(Integer'Image(M))&":"
>------->------->-------&Strip(Integer'Image(S));
>-------end To_String;

The first call is To_String(Clock + offset). When an exception occurs,
it is called as To_String(Clock) for the log message. Strip is just a
function that strips off leading white space.

This worked until around midnight. Predictably, I got a constraint
exception when assigning the value to H, because my limits are wrong.
However, when printing the exception message, this function is called
again[1], and returned the result of "24:0:0". I am kind of confused
this is possible, unless Duration was initially 86_400.0[2].

Maybe somewhere my logic is flawed, I will investigate again tomorrow.

Notes:
[1] hmmm... what happens if you get a recursive exception in Ada?
    I probably should protect my logging functions a bit better.
[2] Can someone confirm my assumption that Integer(86_399.9) = 86_399?
-- 
Brian May <bam@snoopy.apana.org.au>