Interesting talk on Python vs. Ruby and how he would like Python to have just a bit more syntactic flexibility.
Steve Howell
showell30 at yahoo.com
Fri Feb 19 05:46:04 CET 2010
On Feb 18, 2:49 pm, Jonathan Gardner <jgard... at jonathangardner.net>
wrote:
> On Feb 18, 8:15 am, Steve Howell <showel... at yahoo.com> 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
>
> If this style of programming were useful, we would all be writing Lisp
> today. As it turned out, Lisp is incredibly difficult to read and
> understand, even for experienced Lispers. I am pleased that Python is
> not following Lisp in that regard.
>
> for n in range(1,6):
> square = n*n
> cube = n*n*n
> if square == 25 or cube == 64: continue
> print cube
There's definitely a cognitive dissonance between imperative
programming and functional programming. It's hard for programmers
used to programming in an imperative style to appreciate a functional
approach, because functional solutions often read "upside down" in the
actual source code and common algebraic notation:
def compute_squares_and_cubes(lst):
return [(n * n, n * n * n) for n in lst]
def reject_bad_values(lst):
return [(square, cube) for (square, cube) \
in lst if not (square == 25 or cube == 64)]
def cubes_only(lst):
return [cube for square, cube in lst]
def print_results(lst):
# 1. compute_squares_and_cubes
# 2. reject_bad_values
# 3. take cubes_only
# 4. print values
for item in \
cubes_only( # 3
reject_bad_values( # 2
compute_squares_and_cubes(lst))): # 1
print item # 4
You can, of course, restore the natural order of operations to read
top-down with appropriate use of intermediate locals:
def print_results(lst):
lst2 = compute_squares_and_cubes(lst)
lst3 = reject_bad_values(lst2)
lst4 = cubes_only(lst3)
for item in lst4:
print item
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