[mercury-users] Puzzled about about I/O in predicates which may fail

[Ralph Becket]

Gregory D. Weber, Tuesday, 23 November 2004:
> It seems to me that by using state variables, I can "fix" an
> error involving I/O in predicates which may fail.
> If read_problem_decl_semidet is indeed semidet, then
> 
> (EXAMPLE 1)
> 
> main(!IO) :-
> 	(
> 	  read_problem_decl_semidet("credit.decl", Problem, !IO) ->
> 	  describe_problem(Problem, !IO)
> 	;
> 	  io__print("Error reading file\n", !IO)
> 	).
> 
> compiles without any error message.  Moreover, running the program
> actually works!

This is a bug!  Thank you for reporting it; I'll look into what's going
on as soon as I get a few spare minutes.

-- Ralph
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