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From: guy%gorodish@Sun.COM (Guy Harris)
Newsgroups: comp.lang.c
Subject: Re: Function prototypes versus open()
Message-ID: <22196@sun.uucp>
Date: Fri, 26-Jun-87 15:33:08 EDT
Article-I.D.: sun.22196
Posted: Fri Jun 26 15:33:08 1987
Date-Received: Sat, 27-Jun-87 10:53:25 EDT
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> Except that this makes it effectively impossible to use the dispatcher.
> Consider the call to the dispatcher that would have been written (under
> the old K&R paradigm) as
> 
> int fxn();
> ...
> dispatcher(....,fxn);
> 
> How does on write the corresponding thing?

/*
 * This would presumably appear in an #include file.
 */
typedef union {
	int	(*three_argument)(int, int, double);
	int	(*four_argument)(int, int, double, double);
	int	(*five_argument)(int, int, double, double, double);
} function_pointer_passed_to_dispatcher;

int fxn(int x; int y; double z);

extern return_type_of_dispatcher dispatcher(various_argument_types,
    function_pointer_passed_to_dispatcher funcp);

function_pointer_passed_to_dispatcher temporary;

temporary.three_argument = fxn;

dispatcher(..., temporary);

Yes, this may be ugly, but it's type-correct, and may even be necessary
in some implementations.
	Guy Harris
	{ihnp4, decvax, seismo, decwrl, ...}!sun!guy
	guy@sun.com