Re: Perl vs. Python: Looking at the Code

[ariels]

Some good points here:

Multiple implementations are good:

Code should be written to a language spec, not to a particular implementation. Observe how clear ISO C is about "x=x++" (it is undefined behaviour). Perl isn't so clear; what's worse is that, since there's only one implementation, "suck it and see" might be considered a good answer (it isn't, but only because of the possibility of a later implementation changing).

Function parameters

The Perl way makes some nifty things possible, but it doesn't "make the easy things easy".

Docstrings

(Stolen shamelessly from Lisp, of course). Perl doesn't have an interactive mode (but see my RFC 184 for Perl6, which I hope will be approved), but even so docstrings would be nice. Not that PODs are bad...

Some of the points are awful:

Less typing with Python:

No "concrete examples" to show this; a study of a short program implemented in both languages would go a long way to convince Perlers of this. Especially given that the claim is a bit odd -- most Pythoners I spoke to were enamoured of their language's verbosity, and said that made it better than Perl.

But WHY is this a measure of language quality? Surely Perl wouldn't be a better language if we removed length, on the grounds that y///c is one keystroke less?

Here's what put me off Python:

No closures

When people say Perl lacks closures, they mean you have trouble if you define a named sub inside a named sub (and try to return it). Python is much worse, though: it invents a new concept of "scope". You have "outer scope" (globals, really) and "inner scope" (dynamic variables, like local creates in Perl). You cannot write

def adder(x):
  return lambda y: x+y

a = adder(5)
print a(3)

because `x' is lost. The manual says to fudge it with default argument values, by drilling your variables down into the scope:

def adder(x):
  return lambda y,a=x: a+y

This is horrible! After a=adder(5), a(3) gives me 8, but so does a(4,4).

Closures aren't some academic abstraction; for instance, they probably form the basis of the most readable, intuitive style for coding Perl/Tk (or any other GUI).

Regexps

What can I say? Perl does it better. I use regexps a lot; this "little language" is immensely powerful and intuitive.

Surprisingly, most of Python's real advantages have been eliminated, too!

Tuples

Internals said to be "nicer"

If you've ever tried to write any non-trivial XS (or Swig or Inline), you probably cursed Perl. My Pythoneer friends say Python internals are nicer, and better-documented.

Nice mechanism for "obsoleted" and "proposed" language features.