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From: wald-david@CS.YALE.EDU (david wald)
Newsgroups: comp.lang.c
Subject: Re: Union initialization
Message-ID: <51116@yale-celray.yale.UUCP>
Date: 19 Feb 89 20:55:44 GMT
References: <816@atanasoff.cs.iastate.edu> <16019@mimsy.UUCP>
Sender: root@yale.UUCP
Reply-To: wald-david@CS.YALE.EDU (david wald)
Organization: Yale University Computer Science Dept, New Haven CT  06520-2158
Lines: 41

In article <16019@mimsy.UUCP> chris@mimsy.UUCP (Chris Torek) writes:
>In article <816@atanasoff.cs.iastate.edu> hascall@atanasoff.cs.iastate.edu
>(John Hascall) writes:
>>Does 'ANSI' C allow for union initialization?
>
>The rule is (perhaps overly) simple: the first member of the union
>is initialised.  Given
>
>       union { float f; int i; } u;
>
>u.f is 0.0, and u.i is indeterminte.  You may write
>
>       union { float f; int i; } u = { 1.0 };
>
>to set u.f, but you cannot initialise u.i since it is not the first
>member.

I wonder...

Yes, this question deals with some hypothetical C' or C+=2 (not quite D,
since it's a language extension rather than a revision), but...

Would it make the syntax more ambiguous to have allowed

union { float f; int i; } u.i = {1};

?

The only difficulty comes in extending this to structures containing
unions:

struct { char *cp; union { float f; int i; } u; } s = { NULL, ????};

Any suggestions?


============================================================================
David Wald                                              wald-david@yale.UUCP
waldave@yalevm.bitnet                                 wald-david@cs.yale.edu
"A monk, a clone and a ferengi decide to go bowling together..."
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