Re: basic basic ada question

["Jeffrey R. Carter" <spam.not.jrcarter@acm.not.spam.org>]

Robert A Duff wrote:
> 
> Why should one think in C or Ada?  There are lots of concepts that
> transcend the languages.  After all, both languages have subroutines,
> parameter passing, stack/heap allocation, etc, etc.

The Ada mindset is essentially the same as the SW engineering mindset.

> Well, actually, the first argument is numbered 1 in C, too.  ;-)
> argv[0] is what Ada calls Command_Name -- not one of the arguments.

To C, it's one of the arguments (the 1st, so naturally it's numbered 0). 
Ada realizes that it's not. It's the command that the arguments are 
arguments to.

> Dijkstra wrote an interesting paper called "Why numbering should start
> at zero", which you can find via google.  I don't buy it -- I like to
> number most things starting at 1, despite his fairly reasonable
> arguments to the contrary.

I've seen it, and I don't buy it, either. My experience is that fewer 
mistakes are made when the numbering from the domain is used. Some of 
his arguments, such as ease of calculating the length of a sequence, are 
things that the language should do for you. There should be 'Length for 
discrete subtypes; it returns the number of values in the subtype.

> It's interesting that for enumeration types, T'Pos starts numbering
> at 0.

Yes. They're not Pos-itions, they're offsets. Positions should start at 
1. If they did, then T'Base'First could be 0. That might be useful in 
some cases.

-- 
Jeff Carter
"I fart in your general direction."
Monty Python & the Holy Grail
05