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From: etxnisj@eos8c21.ericsson.se (Niklas Sjovall)
Newsgroups: comp.lang.c
Subject: isalpha in ctype.h
Message-ID: <1991Mar20.112543.5515@ericsson.se>
Date: 20 Mar 91 11:25:43 GMT
Sender: news@ericsson.se
Organization: Ericsson Telecom AB
Lines: 17


Hi,

I want to use a macro defined in ctype.h on a Sun4 (4.03), but i don't
fully understand it.

The macro is:
#define	_U	01
#define	_L	02
extern	char	_ctype_[];
#define	isalpha(c)	((_ctype_+1)[c]&(_U|_L))

It's the part (_ctype_+1)[c] i don't understand. Could there be any
segmentation errors using this?

Thanks