Re: Records that could be arrays

[Stephen Leake <stephe_on_the_web@toadmail.com>]

Justin Gombos <rpbkbq.xax.gld@uluv.kbq> writes:

> On 2006-02-23, tmoran@acm.org <tmoran@acm.org> wrote:
>> But with
>>    type Rows is new Local_Float;
>>    type Cols is new Local_Float;
>> the compiler's type checking can point out such errors.  In that case,
>> of course, you have to use a record
>
> Sure, my rule wouldn't apply there because we're no longer talking
> about a composite of a single element type.
>
> Cohen uses x,y coodinates of different types as an example of over
> typing.  I'm kind of on the fence.  I've been declaring every
> dimension within a coordinate system to have the same element type
> because it seems to be more of a hinderance than a benefit to seperate
> them.  The question is whether y is a function of x, 

Or if you want the Cartesian magnitude: sqrt (x**2 + y**2). Or any
other function that involves x and y in a single expression. Like
rotation:

Rotated_Point := (a * Point (x) + b * Point (y), c * Point (x) + d *
   Point (y));

> which can't always be answered when the type comes into existence.

If it's a _point_, we already know about such things. If it's a
genuinely new type, yes, it might be unclear.

-- 
-- Stephe