Re: Case sensitivity (was Re: no title)

[James Rogers <jimmaureenrogers@att.net>]

Stephen Leake <Stephe.Leake@nasa.gov> wrote in news:ullwgh20s.fsf@nasa.gov:

> Hyman Rosen <hyrosen@mail.com> writes:
> 
>> If I'm not mistaken, the following code *does* compile.
>> 
>>      for index in my_array'range loop
>>          declare
>>              Index : integer := 27;
>>          begin
>>              if my_array ( Index ) > current_maximum
>>              then
>>                  current_maximum := my_array ( index );
>>                  Index := index;
>>              end if;
>>          end;
>>      end loop;
> 
> Yes, it does, and it has a bug. If the language was not
> case-sensitive, the bug would be easier to see.
> 

When I place this snippet into a real program I do get a clean
compile. The program does generate an exception at run time on
the first loop iteration.

with Ada.Text_Io;
use Ada.Text_Io;
procedure Badloop is 
   type Foo_Array is array (1 .. 10) of Integer; 
   My_Array        : Foo_Array := (10, 9, 8, 7, 6, 5, 4, 3, 2, 1);  
   Current_Maximum : Integer   := 1;  
begin
   for Index in My_Array'range loop
      declare
         Index : Integer := 27;  
      begin
         if My_Array ( Index ) > Current_Maximum
               then
            Current_Maximum := My_Array ( Index );
            Index := Index;
         end if;
      end;
   end loop;
   Put_Line("Current_Maximum:" & Integer'Image(Current_Maximum));
end Badloop;
    
Note that the above bad code is not solved by making your
language case sensitive.

A C example:

for(i = 0; i < 9; ++i) {
   int i = 27;
   if (My_Array[i] > currentMaximum) {
      currentMaximum = My_Array[i];
      i = i;
   }
{

The C compiler will compile this program without error.
The difference is that the C compiler will allow you to
access beyond the end of the array with no complaints.
In fact, this program will run for an at least one full
iteration, and possibly more. 

Ada still ends up being safer than C because it prevents
array bounds violations at run-time.

Jim Rogers