Re: [avr-gcc-list] Code Optimisation question re: volatile

[D. Daniel McGlothin]

See Dennis Ritchie's C Reference Manual (May 1975)
http://cm.bell-labs.com/cm/cs/who/dmr/cman.pdf, bottom of page 8.

See Eric Huss's 1997 The C Library Reference Guide
http://www.acm.uiuc.edu/webmonkeys/book/c_guide/ section 1.5.5.

The two references differ as to the arrangement of the assignment and
operator tokens.

In brief,

pwm_state ^= _b00000011

'expands' to

pwm_state = pwm_state  ^ _b00000011


If you are interested in some history of C, pop up one and two levels from
that url.

HTH,
Daniel


----- Original Message -----
From: "Svein E. Seldal" <address@hidden>
To: "David Brown" <address@hidden>
Cc: <address@hidden>
Sent: Friday, 23 July 2004 06:14
Subject: Re: [avr-gcc-list] Code Optimisation question re: volatile


> A little question on the side:
>
> David Brown wrote:
> >     pwm_state ^= _b00000011;
>
> Is this syntax standard C? I've never seen this before...
>
>
> Regards,
> Svein
>
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>