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4.1.2 Slices

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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

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slice::= prefix(discrete_range)
Name Resolution Rules

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

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

Static Semantics

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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.

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

Dynamic Semantics

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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

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 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.

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 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

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Examples of slices:

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       Stars(1 .. 15)        −−  slice of 15 characters    (see 3.6.3)
       Page(10 .. 10 Size) −−  slice of Size components    (see 3.6)
       Page(L)(A .. B)       −−  slice of the array Page(L)    (see 3.6)
       Stars(1 .. 0)         −−  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 is in .. 15