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Date: Sat, 18 Jun 2011 13:56:58 +0200
From: Francois Grieu <fgrieu@gmail.com>
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To: lee <lee@yun.yagibdah.de>
Subject: Re: filters
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Xref: x330-a1.tempe.blueboxinc.net comp.lang.c:6350

On 18/06/2011 12:15, lee ask:
 > How do you go about writing a filter, i. e. a program that reads
 > data from stdin and processes it?

#include <stdio.h>
int main(void)
{
int c;
while(EOF!=(c = getchar()))
	{
	if (c>='0'&&c<='9')
		c = '9'-c+'0';
	putchar(c);
	}
}


As an aside, I wonder if
	c = '9'-c+'0'
is safe, and think
	c = '9'+'0'-c
is not.

   Francois Grieu