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From: Kilgallen@eisner.decus.org.nospam (Larry Kilgallen)
Subject: Re: How to make like Fortran "do i = 1,20,2"
Date: 2000/07/27
Message-ID: <T47$ewqox+R8@eisner.decus.org>#1/1
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References: <8lpcbe$40n$1@news.uit.no>
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 27 Jul 2000 13:31:42 GMT)
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Newsgroups: comp.lang.ada
Date: 2000-07-27T00:00:00+00:00
List-Id: <comp.lang.ada>

In article <8lpcbe$40n$1@news.uit.no>, reinert@ola.npolar.no (Reinert Korsnes) writes:
> 
> Hi,
> 
> How can one in Ada elegantly make a loop through each 2 element of an array ?  
> I am looking for something like: "do i = 1,20,2" in Fortran, or
> 
> for I in A'range ("step 2") loop
>    something...
> end loop;

===========

for I in A'range loop
    if (I - A'first) mod 2 = 0
    then
        null;
    end if;
end loop;

But of course that does nothing to ensure that A'length is an even number.

===========

for I2 in A'first/2 .. A'last/2 loop
    declare
        I : INTEGER := I2*2;
    begin
        null;
    end;
end loop;

That approach will have problems if either A'length is an odd
number or if either limit of A'range is an odd number.

===========

But what does Fortran do in those negative and odd number cases ?