[Tutor] Text processing and functional programming?

[Karl Pflästerer]

On 14 Aug 2003, Danny Yoo <- dyoo at hkn.eecs.berkeley.edu wrote:

[great stuff]

> I still think, though, that it's worthwhile to know how to use functional
> programming techniques, sooner or later, because there are some very cool
> things that are possible with them.  Functional programmers often focus on
> writing small, well-defined functions, and more importantly, know how to
> make functions that can create other functions.  Here's a small example:

> ###
>>>> def make_mapper(function):
> ...     def new_function(L):
> ...         return [function(x) for x in L]
> ...     return new_function
> ...

And further on think about closures.  They allow nice constructs (people
who know Common Lisp or Scheme use them all the time).

In [2]: def make_counter(start=0, step=1):
   ....:     def cfun(step=step, counter=[start]):
   ....:         counter[0] += step
   ....:         return counter[0]
   ....:     return cfun
   ...: 

In [3]: c = make_counter()

In [4]: c()
Out[4]: 1

In [5]: c()
Out[5]: 2

In [6]: d = make_counter(10,2)

In [7]: d()
Out[7]: 12

In [8]: d()
Out[8]: 14



   Karl
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