Vote on PEP 308: Ternary Operator
Beni Cherniavsky
cben at techunix.technion.ac.il
Mon Mar 3 09:49:38 CET 2003
On 2003-03-02, Anders Hammarquist wrote:
> Hmm, there was the Q option (fill-in). So if nothing else, you can always
> come up with 3 randomly horrendous syntaxes, and then reject those three.
> Of course, you also have to just how horrendous you syntax is...
>
Hey, that's easy <wink>:
$$
x_\lambda =
\begin{cases}
x & \text{if $\lambda$ is an eigenvalue;}\\
-x & \text{if $-\lambda$ is an eigenvalue;}\\
0 & \text{otherwise.}
\end{cases}
$$
http://www.math.harvard.edu/texman/node26.html#SECTION00089000000000000000
As long as you keep the TeX flavour, it's still unacceptably
unpythonic. E.g.:
x[l] = cases { x if eigenvalue(l),
-x if eigenvalue(-1),
0 otherwise }
Oops, wait, that's not that bad :-). The ``cases`` keyword can be
omitted and the braces should perhaps become parentheses...
To make it horrendously unaceptable (but readable, after all I'm
mimicing math notation), let's do ascii art <;->:
x[l] = / x if eigenvalue(l),
| -x if eigenvalue(-1),
\ 0 otherwise
(there is variable number of ``|`` lines; you can't go lower than two
options, since then the construct is redudant).
--
Beni Cherniavsky <cben at tx.technion.ac.il>
True elegance has negative overhead so it isn't subject to tradeoffs.
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