Date: Fri, 10 Aug 2001 11:28:01 -0400 From: Leo Bicknell <bicknell@ufp.org> To: "hackers@FreeBSD.ORG" <hackers@FreeBSD.ORG> Subject: Re: the =+ operator Message-ID: <20010810112801.A21795@ussenterprise.ufp.org> In-Reply-To: <200108101446.HAA99867@safety.net>; from les@safety.net on Fri, Aug 10, 2001 at 07:46:16AM -0700 References: <3B73F0BC.548D40B3@home.com> <200108101446.HAA99867@safety.net>
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Ok, I had to go try this out for my own:
% cat test.c
int main(void) {
int a, b;
a = 1;
printf("a = %d\n", a);
a += 1;
printf("a = %d\n", a);
a =+ 1;
printf("a = %d\n", a);
a = +1;
printf("a = %d\n", a);
b = 1;
a =+ b;
printf("a = %d\n", a);
a =- b;
printf("a = %d\n", a);
}
% cc -Wall test.c
test.c: In function `main':
test.c:7: warning: implicit declaration of function `printf'
test.c:17: warning: control reaches end of non-void function
% ./a.out
a = 1
a = 2
a = 1
a = 1
a = 1
a = -1
I don't know how hard this would be to do in the compiler, but
perhaps there should be a warning available for "a =+ b", but not
for "a = +b". Maybe that would be better done in lint? I have to
think 99% of the the times this shows up in a program it's a
bug/mistake.
Check out the reference below. In particular, the indent source
is interesting, as is bc.
% find . -name "*.[ch]" -print | xargs fgrep "=+"
./contrib/bc/bc/util.c: printf ("Old assignment operatiors are valid. (=-, =+, ...)\n");
./contrib/cvs/src/wrapper.c: for(temp=++line;*line && (*line!='\'' || line[-1]=='\\');++line)
./contrib/libpam/libpam/pam_misc.c: for (end=++from; *end && *end != ']'; ++end) {
./contrib/nvi/vi/vs_msg.c:#define DIVIDESTR "+=+=+=+=+=+=+=+"
./contrib/tcp_wrappers/percent_x.c: static char ok_chars[] = "1234567890!@%-_=+:,./\
./lib/libc_r/uthread/uthread_kern.c: _thread_run->last_inactive =+
./lib/libc_r/uthread/uthread_kern.c: _thread_run->last_inactive =+ UINT_MAX + 1;
./lib/msun/src/e_asin.c: /* asin(1)=+-pi/2 with inexact */
./lib/msun/src/e_asinf.c: /* asin(1)=+-pi/2 with inexact */
./lib/msun/src/e_atan2.c: case 1: return y; /* atan(+-0,+anything)=+-0 */
./lib/msun/src/e_atan2f.c: case 1: return y; /* atan(+-0,+anything)=+-0 */
./lib/msun/src/e_rem_pio2.c: if(ix<0x4002d97c) { /* |x| < 3pi/4, special case with n=+-1 */
./lib/msun/src/e_rem_pio2f.c: if(ix<0x4016cbe4) { /* |x| < 3pi/4, special case with n=+-1 */
./lib/msun/src/e_sqrt.c: return x*x+x; /* sqrt(NaN)=NaN, sqrt(+inf)=+inf
./lib/msun/src/e_sqrtf.c: return x*x+x; /* sqrt(NaN)=NaN, sqrt(+inf)=+inf
./lib/msun/src/s_erf.c: return (double)(1-i)+one/x; /* erf(+-inf)=+-1 */
./lib/msun/src/s_erff.c: return (float)(1-i)+one/x; /* erf(+-inf)=+-1 */
./lib/msun/src/s_log1p.c: if(x==-1.0) return -two54/zero; /* log1p(-1)=+inf */
./lib/msun/src/s_log1pf.c: if(x==(float)-1.0) return -two25/zero; /* log1p(-1)=+inf */
./lib/msun/src/s_tanh.c: if (jx>=0) return one/x+one; /* tanh(+-inf)=+-1 */
./lib/msun/src/s_tanhf.c: if (jx>=0) return one/x+one; /* tanh(+-inf)=+-1 */
./release/picobsd/tinyware/oinit/oinit.c: printf("\n\n+=========================================================+\n");
./release/picobsd/tinyware/oinit/oinit.c: printf("+=========================================================+\n\n");
./usr.bin/indent/lexi.c: *e_token++ = '='; /* Flip =+ to += */
./usr.bin/indent/lexi.c: *e_token++ = '='; /* Flip =+ to += */
./usr.sbin/pcvt/vttest/main.c:ESC 1! 2@ 3# 4$ 5% 6^ 7& 8* 9(
0) -_ =+ `~ BS
--
Leo Bicknell - bicknell@ufp.org
Systems Engineer - Internetworking Engineer - CCIE 3440
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