[m-dev.] diff: io__call_system/4

[Thomas Charles CONWAY]

Andrew Bromage, you write:
> I've been having a think about this.  Perhaps a better solution is to
> turn io__error into a discriminated union type internally.
> 
> :- type io__error
> 	--->	message(string)
> 	;	signal(int).
> 
> io__error_message(message(Msg), Msg).
> io__error_message(signal(S), Msg) :-
> 	string__format("Aborted with signal %i", [i(S)], Msg).

When we start aiming for thorough, robust I/O we should make
the errno available (either as an int, or an enum, or something)
in error messages.

Thomas
-- 
ZZ:wq!
^X^C
Thomas Conway               				      conway at cs.mu.oz.au
AD DEUM ET VINUM	  			      Every sword has two edges.