[mercury-users] Way to exit immediately from a Mercury program?

[Michael Day]

Hi Nicholas,

> To exit from the Zinc compiler when something like a bad option name is
> encountered.  Currently I have to make sure that the if-then-elses are done
> in such a way that if a bad option is encountered then no real code follows
> the bad-option-handling code before the end of main/2 is hit.

main(!IO) :-
    command_line_arguments(Args, !IO),
    parse_options(Args, Res),
    (
        Res = ok(Options),
        main(Options, !IO)
    ;
        Res = error(Error),
        write_string(Error++"\n", !IO)
    ).

Keep your predicates very small, then no problem :)

Michael

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