[Python-Dev] Trinary Operators

[Guido van Rossum]

> Notwithstanding which, I occasionally wish that Python had an
> if-then-else operator.

Me too, on odd-numbered days.  (On even-numbered days I think the
addition to the learning curve isn't worth the savings in typing.)

> I personally like the way Algol 68 does it, although I acknowledge
> that Python couldn't really do it the same way because Algol 68
> does not distinguish between statements and expressions.
> 
> Algol 68 always uses closing-delimiter keywords to go with the
> corresponding opening-delimiter keywords, so an if-expression
> looks like this:
> 
>         if ... then ... fi
>         if ... then ... else ... fi
>         if ... then ... elif ... then ... fi
>         if ... then ... elif ... then ... else ... fi
> 
> and so on (I think it's spelled "elif", but it might be "elsf" --
> it's been a long time since I studied Algol 68).

It's elif.

> What I find particularly nice is that Algol 68 allows "if" to be
> abbreviated as "(", "fi" as ")", "then" or "else" as "|", and
> "elif" as "|:".
> 
> So where a C programmer would write
> 
>         x = (y>z? y: z);
> 
> an Algol 68 programmer would write
> 
>         x := if y>z then y else z fi;
> 
> or, equivalently
> 
>         x := (y>z | y | z);
> 
> Of course, using | this way works only because Algol 68 uses
> different symbols for "and" and "or".

I think I've seen the suggestion

    x = (y if y>z else z)

:-)

--Guido van Rossum (home page: http://www.python.org/~guido/)