Re: Improving Ada's image - Was: 7E7 Flight Controls Electronics

["Robert I. Eachus" <rieachus@comcast.net>]

Hyman Rosen wrote:

> No, it's a complete hash. Isn't it wrong as well? It claims that 0
> can't be used as a lower bound for String.

Why ask here?  You can write a couple of lines in Ada, and look at the 
error message you get.

Now, putting on my language lawyer hat Hyman is "correct" but for normal 
use the tutorial is fine.  You can define a null String in Ada as:

Foo: String(0..-1);

and while declaring:

Bar: String(0..1) := "  ";

is legal most compilers will provide a warning that Constraint_Error 
will be raised at run time.  With GNAT 3.15p, the program:

procedure String_Test is
   Foo: String(0..-1);
   Bar: String(0..1) := "  ";
begin null; end;

Compiles, but with the warning:
string_test.adb:3:15: warning: static value out of range of type 
"Standard.Positive"
string_test.adb:3:15: warning: "Constraint_Error" will be raised at run time

> This "tutorial" is exactly
> what I was talking about - something which will utterly confuse C
> programmers, because it does nothing to address them on terms they
> understand, having come from an environment where strings are
> variable-sized sequences within fixed-length buffers, with a null
> character as an end marker.

So it tells them to use Ada.Strings.Unbounded: "To overcome the 
constraint problem for strings Ada has a predefined package 
Ada.Strings.Unbounded which implements a variable length string type." 
Again, as a language lawyer, I would suggest both Bounded and Unbounded 
and explain the differences, but that is not the object of this tutorial.

-- 

                                           Robert I. Eachus

The ideology he opposed throughout his political life insisted that 
history was moved by impersonal tides and unalterable fates. Ronald 
Reagan believed instead in the courage and triumph of free men and we 
believe it all the more because we saw that courage in him.  -- George 
W. Bush June 11, 2004