Fri, 22 Nov 2002 17:45:41 GMT
> From: [log in to unmask]
> i had a small doubt regarding the size occupied by the variable of a
> boolean type.
> x : boolean;
> put(boolean'size); -- it is giving 1 bit
> put(x'size); -- it is returning 8 bits
> why is it so?
'Size is the minimum required, clearly a Boolean will fit in 1 bit if
it's packed in. However, if the compiler can generate more efficient
code by putting actual instances in a byte (or more) it can do so.
X'Size is the size of the actual object, 8 bits -> 1 byte.
If X'Size was 1, what would the compiler do with the other 7 bits in
the byte, given it probably couldn't use them for anything else?
You might look in the ALRM for 'Max_Size_In_Storage_Elements or in the
GNAT documentation for 'Object_Size.
> actuallly i want to type cast a array of boolean type into an integer
> type arr_type is array(integer range 1..2) of boolean;
> function uncheck is new unchecked_conversion(arr_type,integer);
> a(1) := TRUE
> a(2) := TRUE
> when converted, the value i am getting is 257 instead of 3
I guess you are running on an Intel machine? (probably not a VAX or an
Alpha). You have 2 array elements each of one byte, each with value 1
(for True), 256*1 + 1 -> 257.
Didn't your compiler complain about the other 2 bytes? (most compilers use
4 byte Integers nowadays).
Check out pragma Pack and the record representation attributes (ALRM
I do wonder just what you're trying to achieve with this code, sounds