question about the fate of input stream after DATA_ERROR

[ucsbcsl!lemon.ucsb.edu@ucbvax.Berkeley.EDU (Maxwell Lee)]

Hi, I have some ADA code which produces a strange result I can't understand
why.  I'm wondering if someone out there in ADA-land can help me.

I have the following code:

                   type OPCODE is (I, S, Q, X);
                   CODE: OPCODE;
-------------------------------------------------
(in my main program)
         with TEXT_IO; use TEXT_IO;
         with INTEGER_IO; use INTEGER_IO;
         package OPCODE_IO is new ENUMERATION_IO(OPCODE); use OPCODE_IO;
--------------------------------------------------
                   
I simply want to perform a            GET(CODE);
from standard-input.

When I enter an "i", "s", "q", "x", "I", "S", "Q", or "X" the command
works fine.

When I enter a number, say "1", a DATA_ERROR is raised, but the "1" is
left in the input stream (input buffer).

When I enter a character that's not an OPCODE, say an "m", a DATA_ERROR is
raised, but the "m" is removed from the input stream (input buffer) !!!

I understand why both a "1" or an "m" will produce DATA_ERROR, but
I don't understand why "1" will be left in the input stream, but "m"
will be removed from the input stream.  I assumed that in both cases
it would be left in the input stream.  Can someone help me?
Thank you.

**********************************************************************
"Mongo don't know .... Mongo only pawn in game of life."
(From the movie "Blazing Saddles")

maxwell@cs.ucsb.edu
**********************************************************************