Ada Programming/Attributes/'Range


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DescriptionEdit

The meaning of the attribute depends on the meaning of the prefix X.

If X is a scalar subtype, X'Range represents the range of valid values for that subtype, i.e. it is the same as the subtype itself.

If X is a constrained array subtype or an array object, X'Range denotes the index range of X.

In any case, X'Range is equivalent to X'First .. X'Last, but X is only evaluated once.

If X is multidimensional, the attribut needs a static parameter N to identify the N-th index; 'Range (1) is the same as 'Range.

X'Range (N) is equivalent to X'First(N) .. X'Last(N), but X is only evaluated once.

ExamplesEdit

type T is range 1..10;  -- T'Range is equal to T
type A is array (T) of S;                  -- these three     A'Range is the same as T
type A is array (T'Range) of S;            -- declarations
type A is array (T'First .. T'Last) of S;  -- are equivalent

type B is array (T range <>) of S;  -- B'Range is illegal (B is unconstrained)
subtype SB is B (2 .. 5);           -- SB'Range is the same as 2 .. 5

type M is array (Boolean, T) of S;  -- M'Range is equivalent to M'Range (1), which is Boolean
                                    -- M'Range (2) is the same as T

OA: A;           -- OA'Range is the same as T
OB: B (2 .. 5);  -- OB'Range is equal to 2 .. 5

See alsoEdit

WikibookEdit

Ada Reference ManualEdit

Last modified on 19 March 2014, at 13:51