Re: C Unions

Ok, why would you do this?

Thanks,
Elizabeth (another C illiterate)

At 06:53 PM 10/30/2000 -0500, you wrote:
>Hi Mike:
>
>You wrote:
> >
> > Could anyone explain to a C illiterate how to interpret a C class union?
> >
>
>A union in C gives the bytes in question "multiple personalities". As
>far as the compiler is concerned the names refer to the same bytes. if
>you call
>
> > For example:
> >
> > -------------------------------------------------
> > typedef struct _PROPSHEETPAGE {
> > DWORD dwSize;
> > DWORD dwFlags;
> > HINSTANCE hInstance;
> > union {
> > LPCSTR pszTemplate;
> > LPCDLGTEMPLATE pResource;
> > };
>
> Here you can refer to _PROPSHEETPAGE.pszTemplate or
>_PROPSHEETPAGE.pResource and you will get the data at the same
>address. If one of the types is larger than the other the larger
>number of bytes would be allocated and of course the extra bytes would
>be unused when storing a smaller type. But
> >
> > -------------------------------------------------
> > CLASS PROPSHEETPAGE
> > VARIABLE dwSize
> > VARIABLE dwFlags
> > VARIABLE hInstance
> > \ union
> > VARIABLE pszTemplate
> > VARIABLE pResource
>
>this will not work correctly. You need only one variable for each of
>the unions (provided the type is covered by four bytes.
>
>And noe the ubiquitous HTH :)
>
>--
>John McKeon
>jmck_at_customsightsound.com
>
>_______________________________________________
>Sftalk mailing list Sftalk_at_forth.com
>Visit Sftalk on the web at http://www.forthinc.com/mailman/listinfo/sftalk

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Elizabeth D. Rather (US & Canada) 800-55-FORTH
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Received on Mon Oct 30 2000 - 16:18:12 PST