Re: loop step function

[johnherro@aol.com]

Perhaps there's also another reason that a STEP clause was deliberately
omitted from Ada.  In many languages, the index of the FOR loop has to be
a numeric (integer in most languages, but in Basic it may also be a
float).  However, in Ada the index could be any discrete type, such as an
enumeration type.  It doesn't have to be numeric.  Here's my favorite
emumeration type:

type CLA_Message_Type is (Ask_For _Help, Give_Help, Discuss_Ada,
Please_Do_My_Homework, Flame, Flame_The_Flamer);

Now in Ada you could write

for L in Ask_For_Help .. Flame loop

just as easily as you could write "for J in 1 .. 10 loop".  It would make
sense to allow a STEP 2 clause for J, because you could add 2 to J.  But
you certainly couldn't add 2 to L.  No STEP clause would make sense for L.
 For consistency, Ada doesn't allow a STEP clause for any FOR loop, even
if the index is numeric.

The reason pointed out earlier, that incorrect loop termination is a
frequent source of error, is certainly another valid reason why Ada
deliberately omitted the STEP clause.

- John Herro
Software Innovations Technology
http://members.aol.com/AdaTutor
ftp://members.aol.com/AdaTutor