Small Troll on notation of variables over time

[Hendrik van Rooyen]

Hi there,

I can write:

s = 'some string'
then print s[1] will be the string 'o'

and a while later I can write:

s = 'other some string'
then print s[1] will be the string 't'

and then:

s = [1,2,3,4]
then print s[1] will be the number 2

and still later:

s = {1:'boo',2:'foo',3:'shoo'}
when print s[1] will yield the string 'boo'

Now how about introducing an index that works over time,
such that s{0} (the default so as to not break any existing code)
implies the current object bound to the name s,
with s{1} being the previous one, and so on...

This will mean that s{2}[1] is the string 't'
and s{3}[1] is the string 'o'
while s{4} should be None...

It should be easy to implement this, as all that needs to be done is to
change the "pointer" (or whatever) to the object with a stack of them
at the time the binding or rebinding is done...

I first thought of using s{-1} for the previous "value" but that
suffers from the regrettable disadvantage that it implies the
existence of an s{1} - i.e. a future value - and I could not think
of a way to achieve this - so the minus sign adds no information
and should therefore be left out...

What do you guys think?

- Hendrik

[Chris Johnson]

Hendrik van Rooyen wrote:

Hi there,

I can write:

s = 'some string'
then print s[1] will be the string 'o'

and a while later I can write:

s = 'other some string'
then print s[1] will be the string 't'

and then:

s = [1,2,3,4]
then print s[1] will be the number 2

and still later:

s = {1:'boo',2:'foo',3:'shoo'}
when print s[1] will yield the string 'boo'

Now how about introducing an index that works over time,
such that s{0} (the default so as to not break any existing code)
implies the current object bound to the name s,
with s{1} being the previous one, and so on...

This will mean that s{2}[1] is the string 't'
and s{3}[1] is the string 'o'
while s{4} should be None...

It should be easy to implement this, as all that needs to be done is to
change the "pointer" (or whatever) to the object with a stack of them
at the time the binding or rebinding is done...

I first thought of using s{-1} for the previous "value" but that
suffers from the regrettable disadvantage that it implies the
existence of an s{1} - i.e. a future value - and I could not think
of a way to achieve this - so the minus sign adds no information
and should therefore be left out...

What do you guys think?

I think it's pointless. If you want access to more than one of these
variables, don't use the same name.

That and if a symbol is still in scope, then all of its previous values
still have active references, so they won't get deallocated by the
garbage collector, meaning a lot of overhead that most people will not
take advantage of.

[John Machin]

Hendrik van Rooyen wrote:
[snip]

What do you guys think?

The subject said it all. You should find some other way of entertaining
yourself on the weekends :-)

[Hendrik van Rooyen]

"John Machin" <sj******@lexicon.netwrote:

|
| Hendrik van Rooyen wrote:
| [snip]
| What do you guys think?
|
| The subject said it all. You should find some other way of entertaining
| yourself on the weekends :-)

This is the right answer...

*grin* - well - at least you *were* warned... - Hendrik

[Jeremy Sanders]

Hendrik van Rooyen wrote:

What do you guys think?

You could get something similar using an object, such as

class Hist(object):

def __init__(self):
self.vals = [None]

def __call__(self, index=-1):
return self.vals[index]

def set(self, val):
self.vals.append(val)

a = Hist()

a.set(5)
print a()

a.set('hi there')
print a()
print a(-2)

Which prints
5
hi there
5

--
Jeremy Sanders
http://www.jeremysanders.net/

[Piet van Oostrum]

You are about 7 months early.
--
Piet van Oostrum <pi**@cs.uu.nl>
URL: http://www.cs.uu.nl/~piet [PGP 8DAE142BE17999C4]
Private email: pi**@vanoostrum.org

[Hendrik van Rooyen]

"Piet van Oostrum" <pi**@cs.uu.nlWrote:

| You are about 7 months early.
| --

Am I? - Early for what - a seven months premature baby is small indeed...

- Hendrik

[Hendrik van Rooyen]

"Jeremy Sanders" <je*******************@jeremysanders.netwrote:

| Hendrik van Rooyen wrote:
|
| What do you guys think?
|
| You could get something similar using an object, such as
|
| class Hist(object):
|
| def __init__(self):
| self.vals = [None]
|
| def __call__(self, index=-1):
| return self.vals[index]
|
| def set(self, val):
| self.vals.append(val)
|
| a = Hist()
|
| a.set(5)
| print a()
|
| a.set('hi there')
| print a()
| print a(-2)
|
| Which prints
| 5
| hi there
| 5

- Sneaky! - I like this....

- Hendrik