Re: Trivial question: how to avoid confusing sec, min, hour and day in a program?

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

Op 6-9-2021 om 11:47 schreef Dmitry A. Kazakov:
> On 2021-09-06 09:20, ldries46 wrote:
>> Op 5-9-2021 om 9:27 schreef Dmitry A. Kazakov:
>>> On 2021-09-05 08:56, reinert wrote:
>>>> Anybody with good ideas on how (in a simplest possible way) to 
>>>> avoid to confuse between representation of time as seconds, 
>>>> minutes, hours and days in an Ada program?
>>>
>>> Just use the standard type Duration.
>>>
>>>> It is somewhere in my program natural/human to think in seconds 
>>>> whereas  minutes or hours feels more natural at other places (so 
>>>> the numerics is "human"). Example to illustrate: heart rate is 
>>>> "natural" to give in number per minute (not in number per second, 
>>>> hour or day). Time on work is normally given by hours (not seconds) 
>>>> etc..
>>>
>>> The user interface is responsible to convert anything to Duration 
>>> and back.
>>>
>> I agree with Dimitry but I think the problem  is far bigger and not 
>> only in Ada but in every computer language. You cannot use packages 
>> written by others if you do not know the dimensions they use. For 
>> instance in mechanical engineering in Europe there is a general use 
>> of cm while in other countries they use inches and in aircraft 
>> engineering they use in Europe mostly mm.
>
> Why do you need that? If written in Ada, the value is of some separate 
> numeric type you could not mix with other types.

I do need that because you can use the same packages in different 
trades. If you want to calculate the inertia of a construction dependent 
on the location or the trade you are working in you use different 
dimension systems. Indeed you can use SI but most mechanical engineers 
use the cm as a basic unit while aeronautical engineers use the mm as 
there basic unit and the result differ with 4 zero's. In the USA they 
probably use inches which differ some incredible factors. if an American 
uses a European standard HE100 element in his calculations he has first 
to recalculate all inertia values. This will lead to greater error 
possibilities.
>
>> In general the use of dimensioning system ( f.i. cgs -cm gram second) 
>> is different for different countries and application area's. Some 
>> factors used within calculations are even dependant in the 
>> dimensioning system.
>> It would be a good idea if a package was developed that can solve all 
>> these problems for instance by doing the calculations in one of the 
>> possible dimensioning systems automagically presenting the results in 
>> the dimension you choose.
>
> If calculations are involved, they are performed in SI, because 
> otherwise you need factors in all formulae. And SI means no mm, but m, 
> no km/h, but m/s etc.
Sorry but It should perhaps be so but it is not. Programs made primarily 
for Aircraft engineering (f.i. CATIA 5/6) do use mm and your velocity 
clock in your car shows km/h and it registers the distance in km (in 
England and the USA mph and miles) In aircraft the Speed is often still 
measured in Knots (Nautical miles per hour). Maybe French aircraft will 
possibly show km/h. It is to hazardous to change this
>
>
>> Such a system must exist of a record for every value, that exist of 
>> at least  real values for the standard dimensioning system and the 
>> value in the dimensioning system you want, the factor between the two 
>> systems and the string containing the dimension, perhaps even more.
>> There should be functions for "+", "-", "*", "/" and sqrt.
>
>    http://www.dmitry-kazakov.de/ada/units.htm
>