Re: Unchecked_Conversion

[Keith Thompson <kst@cts.com>]

rlove@antispam.neosoft.com (Robert B. Love ) writes:
[...]
> My experience runs counter to this.  My employer has chosen to use
> typing for every conceivable measurement. So we have type Meters, 
> Meters_Per_Second, Feet, Feet_Per_Second, Seconds, Watts, Volts, and so 
> on.
> The list is endless.
> 
> To avoid conversions I would have to have hundreds of overloaded 
> operators.
> And to make matters worse, we have generic vectors that can be 
> instantiated
> for the basic types above.  I would have to have overloaded operators for
> all the vector combinations.

At some cost in efficiency, you could use a single type, say Quantity,
implemented as a record that includes the units and a numeric value.
Inconsistent unit errors would raise Constraint_Error rather than
failing at compilation time.

If you write the code carefully enough, you might even be able to
replace the package that defines type Quantity with a more efficient
one that doesn't do the checks (type Quantity is new Long_Float or
whatever).  Use the checking version during development to catch
errors, and use the more efficient version (with thorough testing, of
course) for the released product -- unless the checking version
happens to be fast enough.

Just a thought.

-- 
Keith Thompson (The_Other_Keith) kst@cts.com  <http://www.ghoti.net/~kst>
San Diego Supercomputer Center           <*>  <http://www.sdsc.edu/~kst>
Cxiuj via bazo apartenas ni.