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From: wendt@handel.cs.colostate.edu (alan l wendt)
Newsgroups: comp.lang.c
Subject: casting to a union
Message-ID: <3455@ccncsu.ColoState.EDU>
Date: 13 Dec 89 00:46:39 GMT
Sender: news@ccncsu.ColoState.EDU
Reply-To: wendt@handel.cs.colostate.edu (alan l wendt)
Organization: Colorado State University
Lines: 26

Apologies if this has come up before; I don't follow this group.

I have a function that accepts either char pointers or ints as
arguments, so I declare it with unions,

union numstr {
    int	i;
    char *s;
    };

void foo( union numstr ns ) { ... }


Why can't I call it as follows:

	foo((union numstr)7);

Presumably foo knows which it is getting by some external means.
This seems easy and innocuous, but I don't think the language
will let me do it.
Probably if this were allowed in, the backwards conversion would
also be allowed, i.e. from (union numstr) to (int).  That would
be ok with me, too; I actually prefer "(int)ns" to "ns.i".
Can anybody think of a reason not to allow this?

Alan Wendt