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Defending the ternary operator

Andrew Dalke adalke at mindspring.com
Mon Feb 10 12:58:05 EST 2003 
John Roth:
> So? I've seen people do things the hard way in
> just about every language I've worked in. In most
> cases, all it takes is a friendly suggestion: "Wouldn't
> this way be clearer?" and they go "Huh? Oh!" and
> the problem goes away.

Answer two questions for me:
  1) C/C++ code has the ?: operator.  Why then do people use
      if (cond) {
        x = val1;
      } else {
        x = val2;
      }
when the expression
      x = cond ? val1 : val2;
is "better"?  Ditto for
      if (cond) {
          return val1;
      }
      return val2;

My limited analysis suggests that the first of these options in
C/C++ is used more often than the second one.  That suggests
to me that the ternary if/else operator is not generally considered
more useful or at least more memorable, than if/else statements.

  2) Suppose you saw some code written
        if cond:
            x = val1
        else:
            x = val2

would you suggest that the Python code always be written
    x = val1 if cond else val2
?  When are the tradeoffs?  Eg, we've already seen some
people say that when the lines get too long it is better written
as an if/else statement rather than an if/else expression, so
the answer is not "always"

Or to generalize #2, when should if/else expression be
used and when should it not be used, and how do you
propogate this sense of style and expectations?

                    Andrew
                    dalke at dalkescientific.com
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