“Ryan Paul” segphault@sbcglobal.net schrieb im Newsbeitrag
news:pan.2004.05.12.19.33.22.639514@sbcglobal.net…
>
>In python, we have map, filter, and list comprehensions, all of which
can
be used to manipulate lists in very general ways. In order to do
certain
things, python users have to stack multiple functions into map
statements.
Generally, this is actually pretty simple to do, and makes things
somewhat
intuitive. In ruby, there are a multitude of rather oddly named array
functions that have very specific behaviors, most of which can be used
with blocks to concisely describe extremely sophisticated operations.
In ruby there are a lot of Enumerable functions, not array’s 
What method do you think is oddly named ?
I for one, would say inject() but using reduce() or fold() is equally
non intuitive for me
Its not so much that their names are strange, its the fact that they
exist
at all. In python, lists only have like 8 or 9 functions, and they are
all
pretty standard and self explanatory (append, count, extend, insert,
remove, reverse, and maybe two or three others). Having things like
collect, replace, assoc, and compact built into arrays is something of a
novelty for a python programmer. I’m used to having to do replacement
like
this, for example:
[y for x in listobj if x == z]
Personally, I feel that it is better to have functions that do these
things,
Did you mean to say “methods”? I ask because strictly speaking there are
no functions in Ruby. They are all tied to some instance.
because list comprehensions scale grotesquely, so I prefer the way
ruby does it. Not only does ruby provide a ton of useful functions to
start with, but I can add as many of my own as I want!
Also, the fact that collect doesnt automatically compact really threw me
for a spin. I was using “x.collect {whatever}.compact” until I figured
out
that it is easier to do a reject on the inverse of what I would have put
in a python ‘filter’.
Normally I would first select and then map. That’s more efficient IMHO:
irb(main):015:0> a = %w{a bb ccc}
=> [“a”, “bb”, “ccc”]
irb(main):016:0> a.select {|x| // =~ x}.map {|x| “(#{x})”}
=> [“(a)”, “(bb)”]
irb(main):017:0> a.select {|x| x.length > 2}.map {|x| “(#{x})”}
=> [“(ccc)”]
I added a ‘filter’ function to the array class that
fixes this for me.
It can be far easier if your criterion happens to support ===, like Regexp
does. Use #grep:
irb(main):008:0> a = %w{a bb ccc}
=> [“a”, “bb”, “ccc”]
irb(main):009:0> a.grep(//) {|x| “(#{x})”}
=> [“(a)”, “(bb)”]
You can easily make up your own criterion:
irb(main):010:0> crit = Object.new
=> #Object:0x101a2920
irb(main):011:0> def crit.===(x); x.length > 2; end
=> nil
irb(main):012:0> a.grep(crit) {|x| “(#{x})”}
=> [“(ccc)”]
You can make your life even simpler with:
module Criterion
def self.create(&b)
def b.===(x); call(x);end
b
end
end
irb(main):031:0> a = %w{a bb ccc}
=> [“a”, “bb”, “ccc”]
irb(main):032:0> crit = Criterion.create {|x| x.length > 2}
=> #Proc:0x100c4978@:32(irb)
irb(main):033:0> a.grep(crit) {|x| “(#{x})”}
=> [“(ccc)”]
Additionally, having two different names for the same thing (eg: collect
and map) was initially confusing, but only because i’m not used to such
things. Python would NEVER do that.
Ruby tries to be nice to people coming from different other languages.
Some have map and some have collect.
Regards
robert
···
On Wed, 12 May 2004 18:04:17 +0000, gabriele renzi wrote:
il Wed, 12 May 2004 16:37:42 GMT, Ryan Paul segphault@sbcglobal.net > > ha scritto::
