Re: Slice and Unbounded String

[dewar@merv.cs.nyu.edu (Robert Dewar)]

Pascal asks:

"With the following command :

S := Ada.Strings.Unbounded.Slice (U, 6, 8);

Should S have a range 6 .. 8 or a range 1 .. 3.

For me (after reading the RM) the first solution is the good one.

The answer will told me if GNAT or ObjectAda has a bug :-)"



The range should be 1 .. 3. This is unambiguously clear from the RM.
!.45(1) says

1   The language-defined package Strings.Unbounded provides a private type
Unbounded_String and a set of operations.  An object of type Unbounded_String
represents a String whose low bound is 1 and whose length can vary
conceptually between 0 and Natural'Last.  The subprograms for fixed-length
string handling are either overloaded directly for Unbounded_String, or are
modified as needed to reflect the flexibility in length.  Since the
Unbounded_String type is private, relevant constructor and selector
operations are provided.


Note the important statement here about the low bound being 1. So
all unbounded strings always have a lower bound of 1.

GNAT certainly returns a lower bound of 1 in accordance with the RM
requirement.