[Python-ideas] unify usage of mutable and immutable objects

[David Mertz]

So it sounds like what you want is this:

In [30]: class FrozenSet(frozenset):
    ...:     def pop(self):
    ...:         item = next(iter(self))
    ...:         return item, self-{item}
    ...:

In [31]: a = FrozenSet({1,2,3,4,5})

In [32]: a.pop()
Out[32]: (1, frozenset({2, 3, 4, 5}))


I think I'm +1 on `frozenset` itself growing that method.

On Tue, Feb 28, 2017 at 10:13 AM, 语言破碎处 <mlet_it_bew at 126.com> wrote:

>
> > but what is frozen_tree_set() here,
> frozen_tree_set is my set class.
>
> > frozensets don't have pop or 'ipop'
> "frozen" means we don't modify the object, but we can use it as prototype
> to create new object.
>     e.g. in Haskell:  val {attr = 1} or in Python: namedtuple._replace
> frozensets can have pop(), but the hash implement will be O(n).
>
> > what is ipop?
> when we pop element from frozensets, we get a element and a new set.
>
>
>
> At 2017-02-28 23:19:03, "Ryan Birmingham" <rainventions at gmail.com> wrote:
>
> I'm sorry for the confusion, but what is frozen_tree_set() here, and what
> is ipop? frozensets don't have pop or 'ipop', so my apologies that I'm a
> bit lost here.
>
> -Ryan Birmingham
>
> On 28 February 2017 at 08:59, 语言破碎处 <mlet_it_bew at 126.com> wrote:
>
>>
>> Hi!
>>     I write a '<'-based immutable set class.
>>     But it is quit different from the standard set class.
>>     I wish collections.abc.Set be more friendly to immutable tree sets or
>>     Python add new syntax to unify such difference.
>>
>>
>> good example:
>>     a = []
>>     a += a  # "a" is the original list
>>
>>     a = ()
>>     a += a  # "a" is a new tuple
>>
>> bad example:
>>     a = set()
>>     a.add(1)        # return None; "a" changed
>>     e = a.pop();
>>
>>     a = frozen_tree_set()
>>     a = a.add(1)    # return another set;
>>     e, a = a.ipop() # return two objects instead of one!
>>
>> solution I used:
>>     a <<= 1         # <==> a = a.add(1)
>>     but "a.ipop()" ....
>> my current solution is to write a wrapper class
>>     to turn immutable set into mutable set,
>>     but it is so noisy to box and unbox.
>>
>>
>> solution that I wish:
>>     a :=.add(1)      # "=." mimic "+="; return the result object
>>     e ~ a :=.pop()
>>
>>     d[key] :=.add(1) # in dict
>>
>>
>>
>> if only python add following features:
>> 1) modify the original object
>>     1-0)
>>         1) define:
>>         def .method(self):...
>>         # "." means "intend to modify self"
>>         #       return any thing
>>         # to avoid immutable method
>>         #       which was intended to return new object
>>         #       leave self unchanged
>>
>>         2) invoke:
>>         r = a..method();
>>     1-1) ignore result
>>         # no matter what returned, discard it
>>         a.-.method();           # <==> [a..method(), None][-1]
>>     1-2) return self
>>         # no matter what returned, return self
>>         a.>.method().>.method();# <==> [a..method(), a..method(), a][-1]
>>
>>
>> 2) create new object
>>     2-0)
>>         1) define
>>         # intend to return (result, new object)
>>         def ^method():...
>>
>>         2)invoke:
>>         r, a' = a.^method();
>>     2-1) return other, discard result
>>         a.-^method().-^method();# <==> a.^method()[1].^method()[1];
>>     2-2) assign other to original variable
>>         a=^method();            # <==> a = a.^method()[1];
>>
>> 3) unify both:
>>     a :=.method();
>>     # if   defined ".method" then "a..method();"
>>     # elif defined "^method" then "a = a.^method()[1];"
>>     # elif defined  "method" then "a.method();"
>>     # else error
>>
>>     r ~ a :=.method();
>>     # if   defined ".method" then "r = a..method();"
>>     # elif defined "^method" then "r, a = a.^method();"
>>     # elif defined  "method" then "r = a.method();"
>>     # else error
>>
>>
>>
>>
>>
>>
>>
>>
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>>
>
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