Special variables: Difference between revisions

=={{header|Ada}}==

Ada has no special variables in the standard namespace, nor are any such variables commonplace in packages, almost all are constants or private variables changed through functions.

The closest thing Ada has to special variables are attributes, which are of an object oriented nature dependant on their prefix. Examples:

* When X is of an array type, X'First denotes the first index of the array (Ada arrays are not limited to starting at 0 or 1).

* When X is of a scalar type, X'First denotes the lower bound of that type.

* X'Size gives the number of bits of memory type X is stored as, but can also be assigned to, to force the program to store the type in that number of bits. (Provided its more than the minimum)

* For example, a 2 bit record (structure) X might be stored as a byte by default as a speed optimization, but X'Size := 2; would force it to be stored as two bits.

There are far too many attributes to list here, but a standard informative list can be found in Annex K of the documentation if you have it installed.

Or Here: [http://www2.adacore.com/gap-static/GNAT_Book/html/aarm/AA-K.html Annex K - Language-Defined Attributes]