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From: bt_are_shite@talk21.com (Stella)
Newsgroups: comp.lang.ada
Subject: Newbie Q : Exception handling
Date: Tue, 27 Nov 2001 10:04:42 GMT
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Date: 2001-11-27T23:42:28+00:00
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Hi All,

Having a strange problem using exceptions. It's ( I presume) a pretty
basic question.

Here's the code:-

-- This program does nothing, and is just an example to indicate 
-- the exception handling problem...

with Text_Io, Ada.Integer_Text_Io;
use Text_Io, Ada.Integer_Text_Io;

procedure Exception_Handling2 is
    
    type Units is ( Ins, Ft, Yd, Mil, Mm, Cm, M, Km, Oz, Lbs, G, Kg );
    Num, Deno, Quot : Units;

    package Units_Io is new Enumeration_Io( Units );
    use Units_Io;

begin
    loop
        begin
            Put("Enter num  >"); Get( Num );
            Put("Enter quot >"); Get( Deno );
            
            Quot :=Num;
             exit;
                        
        exception
            when Data_Error => Put_Line("Wrong_d!"); 
            when Constraint_Error => Put_Line("Wrong_c");
            when others => Put_Line("Wrong_o");
        end;
        
        New_Line;
    end loop;
    
    Put("The result is "); Put( Quot,1 ); New_Line;

end Exception_Handling2;

What happens is that if I enter a garbage value ( i.e. hello ), it
traps the data_error problem fine, and asks for the data again, but if
I enter 0 or any number, it traps the error, but just goes round in an
infinite loop, i.e.
	Enter num > 	Wrong_d!

	Enter num > 	Wrong_d!

	Enter num > 	Wrong_d!

	Enter num > 	Wrong_d!

	etc etc etc

i.e. it doesn't stop at the get(), but just seems to skip over that
line. I've tried flush() to maybe get round any buffer problems, but
that does nothing.

I've found it seems to occur when numbers are input when strings  are
expected and vice-versa.

Any pointers would be gratefully recieved...

( I've tried different compilers, but that makes no difference )

Stella