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From: Keith Thompson <kst-u@mib.org>
Newsgroups: comp.lang.c
Subject: Re: High quality resources for learning modern C?
Date: Mon, 05 Jun 2017 15:51:23 -0700
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bartc <bc@freeuk.com> writes:
[...]
> One reason for downloading it again was to see if the preprocessor 
> handling had changed much since MSVC-2008. I changed the program to:
>
> #include <stdio.h>
> int main()
> {
> 	printf("Hello, World! %X\n", 0x1234e-4 );
> 	return 0;
> }
>
> This prints 1234A for the %X item. But some compilers reject 0x1234e-4 
> as a valid expression (ie. 0x1234e minus 4) because they say it's a 
> malformed pp token).

Those compilers are correct.  It's mildly inconvenient, but it's an
unambiguous consequence of the rules specified in the C standard.

>                      But if the mighty Visual C doesn't care, then I'm 
> not going to either in my own preprocessor.

That's up to you.  If you want your implementation to violate the
standard (because Visual C does so or for any other reason), you're free
to accept `0x1234e-4` without complaint as equivalent to `0x1234e - 4`.

-- 
Keith Thompson (The_Other_Keith) kst-u@mib.org  <http://www.ghoti.net/~kst>
Working, but not speaking, for JetHead Development, Inc.
"We must do something.  This is something.  Therefore, we must do this."
    -- Antony Jay and Jonathan Lynn, "Yes Minister"