Re: How to initiate part of a string?

[eachus@spectre.mitre.org (Robert I. Eachus)]

In article <35e3675e.37587430@SantaClara01.news.InterNex.Net> tmoran@bix.com (Tom Moran) writes:

   Quite so, it should have been
     Txt : String(1 .. 100) := (1 ..  27=>' ') & "abcd" & (32 .. 100=>' ');

    That actually is not the same thing.  The bounds of "abcd" are
1..4, but the catenation preserves the lower bound of the leftmost
entry.  So:

    Txt : String(1 .. 100) := (1 ..  27=>' ') & "abcd" & (1 .. 69=>' ');

is equivalent, except for expository purposes.  To create an aggregate
that can initialize the string write:

    Txt2: String(1..100) := (1..27 => ' ', 28 => 'a', 29 => 'b',
                             30 => 'c', 31 => 'd', 32..100 => ' ');

Painful, but at least in this case you get better bounds info.  Better
still try:

    Txt3: String(1..100) := (28 => 'a', 29 => 'b', 30 => 'c', 31 => 'd',
                             others => ' ');

Of course, reality is that if you really need to do something like
this, you would, I hope, use the standard libraries:

    with Ada.Strings.Fixed;use Ada.Strings.Fixed;
    ...
    Txt4: String(1..100) := Overwrite(Source => String'(1..100 => ' '),
                                      Position => 28,
                                      New_Item => "abcd");

Now finally, I can answer the original question.  Note that Source
argument above was provided as an aggregate, I could also have
written, using the "*" function in Ada.Strings.Fixed:

    Txt5: String(1..100) := Overwrite(Source => 100 * ' ',
                                      Position => 28,
                                      New_Item => "abcd");

or if you really insist on partial initialization:

    Junk: String(1..100); -- uninitialized
    Txt6: String(1..100) := Overwrite(Source => Junk,
                                      Position => 28,
                                      New_Item => "abcd");


--

					Robert I. Eachus

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