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4.1.2 Slices

A slice denotes a one-dimensional array formed by a sequence of consecutive components of a one-dimensional array. A slice of a variable is a variable; a slice of a constant is a constant; a slice of a value is a value.

Syntax

   
       slice ::= prefix(discrete_range)

Name Resolution Rules

The prefix of a slice shall resolve to denote a one-dimensional array (after any implicit dereference).

The expected type for the discrete_range of a slice is the index type of the array type.

Static Semantics

A slice denotes a one-dimensional array formed by the sequence of consecutive components of the array denoted by the prefix, corresponding to the range of values of the index given by the discrete_range.

The type of the slice is that of the prefix. Its bounds are those defined by the discrete_range.

Dynamic Semantics

For the evaluation of a slice, the prefix and the discrete_range are evaluated in an arbitrary order. If the slice is not a null slice (a slice where the discrete_range is a null range), then a check is made that the bounds of the discrete_range belong to the index range of the array denoted by the prefix. Constraint_Error is raised if this check fails.

NOTES

(2) A slice is not permitted as the prefix of an Access attribute_reference, even if the components or the array as a whole are aliased. See 3.10.2.

(3) For a one-dimensional array A, the slice A(N .. N) denotes an array that has only one component; its type is the type of A. On the other hand, A(N) denotes a component of the array A and has the corresponding component type.

Examples

Examples of slices:

    
         Stars(1 .. 15)        --  a slice of 15 characters         (see 3.6.3)
         Page(10 .. 10 + Size) --  a slice of 1 + Size components   (see 3.6)
         Page(L)(A .. B)       --  a slice of the array Page(L)     (see 3.6)
         Stars(1 .. 0)         --  a null slice                     (see 3.6.3)
         My_Schedule(Weekday)  --  bounds given by subtype          (see 3.6.1 and 3.5.1)
         Stars(5 .. 15)(K)     --  same as Stars(K)                 (see 3.6.3)
                               --  provided that K is in 5 .. 15

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