When do you use "if ( a = b )"? (was Re: Funny mistake)

[Darren Morbey]

In article <3130 at inews.intel.com>,
           bhoughto at hopi.intel.com (Blair P. Houghton) writes:
>In article <1991Mar19.192416.13756 at unlv.edu>
             grover at lowell.cs.unlv.edu (Kevin Grover) writes:
>>michi at ptcburp.ptcbu.oz.au (Michael Henning) writes:
>>>grover at sonny-boy.cs.unlv.edu (Kevin Grover) writes:
>>>>	#define EQU ==
>>>>	if ( a EQU b)
>>>NO, NO, NO ! Please don't do this.
>#define should _never_ be used to replace existing tokens.
Just as a suggestion, what about:
     #define EQU(l,r) ((l)==(r)) /*...*/ if( EQU(a,b) )
I realize this is rather messy, because it
"contribute[s] nothing to the readability of the code." (Mr. Henning)
It does make the equality different from the assignment without violating
"#define should _never_ be used to replace existing tokens." (Mr. Houghton)

Pardon me for asking, but please define "obfuscation."

P.S.  I would find it useful to #define NOT(a) !(a),
      #define COMPL(a) ~(a), and #define XOR(a,b) ((a)^(b)).
      I have trouble remembering the use of the tilde and
      circumflex.  Again, only a suggestion.