Interesting talk on Python vs. Ruby and how he would like Python to have just a bit more syntactic flexibility.

Steve Howell showell30 at
Sat Feb 20 17:41:10 CET 2010

On Feb 20, 6:13 am, Michael Sparks <spark... at> wrote:
> On Feb 18, 4:15 pm, Steve Howell <showel... at> wrote:
> ...
> >     def print_numbers()
> >         [1, 2, 3, 4, 5, 6].map { |n|
> >             [n * n, n * n * n]
> >         }.reject { |square, cube|
> >             square == 25 || cube == 64
> >         }.map { |square, cube|
> >             cube
> >         }.each { |n|
> >             puts n
> >         }
> >     end
> This strikes me as a terrible example. For example, this is
> significantly clearer:
>     def print_numbers()
>         for n in [1,2,3,4,5,6]:
>             square, cube = n * n, n * n * n
>             if square != 25 and cube != 64:
>                 print n

This is not an exact translation.  My example prints the cubes.  It is
my fault for using "n" as the parameter in the last block.  I would
rename the parameter to cube.

> I /can/ see arguments for ruby style blocks in python, but not for
> this sort of thing, or lisp style quoted expressions[1]. ie I can see
> situations where you have more complex code in real life where they
> will definitely simplify things.
> [1] This is perhaps more appropriate because '(a b c) is equivalent
>     to (quote a b c), and quote a b c can be viewed as close to
>     python's expression "lambda: a b c"
> However, I can also see that in simple situations - such as the
> example you post - they will have a tendency to make code
> significantly less clear/direct.
> I suppose, if I have a choice between something (hard being possible &
> simple code looking simple) and (hard things being simpler & simple
> things looking harder), I'd probably personally choose the former.
> This is not because I don't like hard things being simple, but because
> I think that simple things are more common and making them look harder
> is a mistake.

I agree with much of what you are saying.  The example is indeed
terribly contrived.

I'm not sure I agree that there is anything unclear or undirect about
the Ruby, though.  I've been fairly immersed in Ruby code, so maybe
it's been warping my brain, but once you get over the unfamiliarity of
the syntax, you see that there's actually a rhythm to the code.

Setting aside punctuation and parameter lists, the code clearly
expresses the transformations and actions in the natural order that
you'd do them:

   LIST map

In English, for the list elements, map them to tuples of squares and
cubes, reject the oddballs, take the cube, and print it out.

         [1, 2, 3, 4, 5, 6].map { |n|
             [n * n, n * n * n]
         }.reject { |square, cube|
             square == 25 || cube == 64
         }.map { |square, cube|
         }.each { |cube|
             puts cube

For such a small problem, I agree it's verbose.   But it's also
completely flat--you don't need to use an "if" statement to express
the concept of rejection.

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