Re: Newbie Q

[Martin Dowie <martin.dowie@btopenworld.com>]

Jim Rogers wrote:
>  
> "Larry Luther" <larry.luther.nospam@dolby.com> wrote in news:RkJXe.771
> $OC2.358@newssvr21.news.prodigy.com:
> 
> 
>> 
>>I saw the following example in "Ada Programming" Wiki book:
>>
>>if Temperature >= Degrees'(40.0) then
>>    Put_Line ("It's extremely hot");
>>elsif Temperature in Degrees'(30.0 .. 39.0) then
>>    Put_Line ("It's hot");
>>elsif Temperature in Degrees'(20.0 .. 29.0) then
>>    Put_Line ("It's warm");
>>elsif Temperature in Degrees'(10.0 .. 19.0) then
>>    Put_Line ("It's cool");
>>elsif temperature in Degrees'(0.0 .. 9.0) then
>>    Put_Line ("It's cold");
>>else
>>    Put_Line ("It's freezing");
>>end if;
>>
>>What happens at 29.5 degrees?
>>I'm assuming that "Temperature in Degrees'(20.0 .. 29.0)" will test
>>the interval Temperature >= 20.0 through Temperature <= 29.0.
>>So temperatures between 29.0 and 30.0 will be considered "freezing".
> 
> 
> You are correct.
> This example exhibits a similar error between 29.0 and 30.0 degrees,
> between 19.0 and 20.0 degrees, and between 9.0 and 10.0 degrees.
> 
> The person writing this program was clearly thinking in terms of
> integer arithmetic when he or she was dealing with either floating
> point of fixed point arithmetic.
> 
> The example does not indicate whether Degrees is a fixed point or
> floating point type. This example would work better with a fixed
> point type than with a floating point type because one can always
> know what the minimum delta between two fixed point numbers is.
> The same cannot be said of a floating point number.
> 
> The example properly demonstrates the syntax of the if..elsif..else
> syntax while also creating a logical error. 

or...

it's a very rare fixed point number, where the delta is 1.0.

   type Degrees is delta 1.0 range 0.0 .. 100.0;

Could be a decimal type,

   type Degrees is delta 1.0 digits 4 range 0.0 .. 100.0;

But more likely, it's a bug...

Cheers

-- Martin