YAAO (yet another assignment operator)

[Alan T. Bowler [SDG]]

Just a bit of history.  The original B compiler (the one that evolved
into the Unix C compiler), had more assignment operators.
Back then the form was =<binop> (i.e. =+ =- =& etc).
The operators ===, =<, =>, =<=, and =>= were present.
They were indpendantly dropped by both Waterloo (in subsequent B compilers),
and by Bell Labs in the evolving C compiler.  The reason was simply
that they were never used and made for language clutter.
    The is of course the small point that trying to support every
case of <binop>= means that "<=" becomes ambiguous.
(i.e. a<=b can then mean "set a to 0 if the current value of a is
greater than or equal to b)