The Big Programming Thread - Page 842

On February 12 2017 12:17 Hanh wrote:
These dynamic arrays are allocated from the stack. Unless you can make sure that they are small you shouldn't spend stack space because it's only typically a few K in size.
If you want to allocate dynamically from the stack, there is the function 'alloca'

On February 13 2017 12:09 dsyxelic wrote:
snippet of my code in python:

from array import array
class ListArray:

   maxlength = 100
   elements = array('i')
   last = -1

   def __init__(self):
      self.elements=[0]*self.maxlength

   #return position of last index+1
   def END(self):
      return last+1

   def INSERT(x, p, self):
      if (self.last+1 >= self.maxlength):
         print 'Error: Cannot insert, list is full.'

I'm getting 'AttributeError: 'int' object has no attribute 'last'' on line the first line of my def INSERT

Anyone know why this is? I'm pretty sure I did this correctly but I guess not

   def INSERT(x, p, self):

   def INSERT(self, x, p):

On February 13 2017 12:34 Blisse wrote:


AFAIK

   def INSERT(x, p, self):

should be

   def INSERT(self, x, p):

otherwise you should be calling x.last

On February 13 2017 12:46 Nesserev wrote:

Self has to be the first parameter of your class method, because the object on which the method is called, is always passed as the first argument. (The parameter's name doesn't have to be self though... but you should call it self anyway, because conventions.).

Second, I also noticed that you made maxlength, elements and last class member, so basically every instance of ListArray would share those variables... if you have more than one instance of said class, they'd probably overwrite each other constantly. Instead, instance members should be initialized in the __init__ function, any other class function, or just x.member from the "outside".

class ListArray:

   maxlength = 100  # class member, one per class, shared by all instances

   def __init__(self):
      self.elements=array('i') # instance member, one per instance
      self.last = -1

Basically, instance members have to be tagged on. When you say x = ListArray(), you start out with an "empty" object, and __init__ for ListArray is run, which first adds the elements member, and then the last member.

On February 14 2017 04:07 Shield wrote:
I've been asked if there is any significant technology coming up for computing, but I don't know anything major other than quantum computer. Is there anything else?

On February 14 2017 07:26 travis wrote:
give an infinite subset X in Q that contains no elements in set N
my answer: Q less than 0 (this one seemed easy but it's weird so im checking)

On February 14 2017 07:26 travis wrote:
give an infinite subset X in R that contains no elements in set Q
my answer: the set of irrational numbers? though I know of no actual proof that this set is infinite in size, I am just guessing it is