Re: How unchecked conversion works?

[Keith Thompson <kst-u@mib.org>]

None <none@none.it> writes:
> HI! I'd like to know what the compiler do for represent a simple float
> for example 34,4 delta 0.1 into an integer type for example range
> 1..10 using an Unchecked_Conversion. Thanks!

I'm not quite sure what you mean.  For one thing, a type declared with
"delta" is fixed-point, not floating-point.

Doing an Unchecked_Conversion from floating-point to integer is
unlikely to be useful.  An Unchecked_Conversion from fixed-point to
integer, on the other hand, might be; a fixed-point value is basically
a scaled integer, and Unchecked_Conversion might make sense if you
want to ignore the scaling.  (Nevertheless, you should spend some time
thinking about what problem you're trying to solve, and perhaps come
up with a cleaner way to do it.)

An Unchecked_Conversion call takes an operand of one type and pretends
that it's a value of another type.  This will typically be implemented
in machine code simply by doing nothing.  For example, if Conv is an
instance of Unchecked_Conversion, and X and Y are of appropriate types,
then this:

    X := Conv(Y);

will probably just copy the value of Y into X, just as

    X := Y;

would do if it were allowed.  (Presumably it isn't allowed because X
and Y are of incompatible types; otherwise you wouldn't need to use
Unchecked_Conversion.)

-- 
Keith Thompson (The_Other_Keith) kst-u@mib.org  <http://www.ghoti.net/~kst>
San Diego Supercomputer Center             <*>  <http://users.sdsc.edu/~kst>
We must do something.  This is something.  Therefore, we must do this.