Re: DECAda/VMS - calling GETJPI

[dewar@cs.nyu.edu (Robert Dewar)]

The basic idea here is that type conversion converts the type, but not
the value, of course floating-point to int already violates this somewhat
as Bob points out, but not quite as dramatically.

Consider the following example:

    type x is mod 10;
    subtype y is x range 0 .. 5;

    vy : y;

    vy := y (-4) -- raises constraint error
    vy := y (-6) -- ok, gives result of 4

At the meeting we accumulated a series of odd examples of this kind, and
decided that it is just a bit too weird to have type conversion generating
what amounts to a significant arithmetic computation.

P.S. in my comments in the example above, I am assuming for the moment the
old semantics. In current Ada 95, BOTH assigments to vy raise constraint
error, since -1 is not in the range 0 .. 5.

Actually to be strict, the constraint error is raised by the conversion
because -1 is not in the set of values for modular type x (0 .. 10).