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[1395482647] Reals

Tony Blair Sat 22 Mar 2014 14:04:00 No.958166 View View Reply Original Report

Quoted By:

Why do so many languages include the type of "real" numbers if real numbers are physically impossible to represent in any computer? There are no and will never be realnums in any computer, stop deluding yourselves.

Anonymous

2

Anonymous Sat 22 Mar 2014 14:37:00 No.958168 Report

Quoted By:

hax my anus

Anonymous

3

Anonymous Sat 22 Mar 2014 14:52:00 No.958170 Report

Quoted By:

WTF?

Of course you can represent them in a computer. Even irrational ones. You represent them symbolically

e.g. the Lisp forms

'(sqrt 2)
pi

Represent irrational, real numbers.

Try using a CAS e.g. Maxima or Mathematica and learning how they work.

Anonymous

4

Anonymous Sat 22 Mar 2014 15:05:00 No.958171 Report

Quoted By:

>>3
Try representing pi or e in a computer.
And in many programming languages a realnum is just a misnomer for a limited-precision floating-point number. And that is just lunacy and delusion. 64 bits are not a "real number".

Anonymous

5

Anonymous Sat 22 Mar 2014 16:14:00 No.958173 Report

Quoted By:

>>4
'e
'pi

There, I represented both.

Anonymous

6

Anonymous Sat 22 Mar 2014 16:18:00 No.958176 Report

Quoted By:


In[33]:= 2 * Pi
Out[33]= 2 \[Pi]

In[34]:= 2 * Pi * E
Out[34]= 2 E \[Pi]

In[35]:= Sqrt[2 * E * Pi]
Out[35]= Sqrt[2 E \[Pi]]

In[36]:= N[Sqrt[2 E \[Pi]], 50]
Out[36]= 4.1327313541224929384693918842998526494455219169913

In[37]:= N[Sqrt[2 * E * Pi], 100]

Out[37]= 4.\
1327313541224929384693918842998526494455219169913084515566512537979579\
28513417032362520362455466283

Do you understand yet?

Anonymous

7

Anonymous Sat 22 Mar 2014 16:23:00 No.958177 Report

Quoted By:

In case you don't understand I'll spell it out for you:

Sqrt[2 * E * Pi]

is a computer representation, as an M-expression of a real number. The exact encoding of the M-expression is not really important, but ultimately it is encoded in binary.

The function N evaluates the precise "lossless" (if you will) computer representation of a real number into a lossy decimal representation to some specified amount of digits.

Nevertheless, it is evident that a computer can easily represent, manipulate and compute with, a real number.

Anonymous

8

Anonymous Sat 22 Mar 2014 18:58:00 No.958182 Report

Quoted By:

>>7
An M-expression is no more a real number than the Greek letter pi is the number pi. It is a symbol, not a number.
Even computation of a real number to arbitrary precision does not mean the real number itself is ever represented in computer memory.
There is no precise "lossless", as you call it, computer representation of an arbitrary real number as it would overfill any memory. You are lying.
Thus saying that any programming language has a "real number" type is misleading, arrogant and delusional. Computers have floating-point numbers, sure, but not real numbers.

Anonymous

9

Anonymous Sat 22 Mar 2014 19:05:00 No.958183 Report

Quoted By:

>>1
Rational numbers can easily be represented in a computer program by defining them as the quotient of two integers. Irrational numbers must be, just like IRL, represented by an approximation or a symbol.

Anonymous

10

Anonymous Sat 22 Mar 2014 20:44:00 No.958187 Report

Quoted By:

>>9
But in programming languages that have a realnum type it is not a type of symbols or even rational numbers, but simply floating-point numbers.

Anonymous

11

Anonymous Sat 22 Mar 2014 22:04:00 No.958192 Report

Quoted By:

>>10
those are shit languages

Anonymous

12

Anonymous Sun 23 Mar 2014 02:21:00 No.958215 Report

Quoted By:

>>11
I'm sorry you can't appreciate REAL programming languages.

Anonymous

13

Anonymous Sun 23 Mar 2014 02:22:00 No.958216 Report

Quoted By:

The ``goo nuff'' ``real'' numbers in most programming languages can't even represent 0.1 exactly, let alone real numbers.

Anonymous

14

Anonymous Sun 23 Mar 2014 03:02:00 No.958217 Report

Quoted By:

>>13
0.1
0.0001100110011001100110011001100110011001100110011001100110011001100110011001100110011001100110011001100

Anonymous

15

Anonymous Sun 23 Mar 2014 03:12:00 No.958218 Report

Quoted By:

>>8
Yes, it's not a real number. It's a representation of a real number. Like a machine word can be a representation of integers (a subset of real numbers) or certain decimals (floating point numbers).

A physical entity can never be a number, it can only represent it.

Anonymous

16

Anonymous Sun 23 Mar 2014 03:20:00 No.958219 Report

Quoted By:

A physical entity can never be a number, it can only represent it.
I actually have a seven in my pocket right now.

Anonymous

17

Anonymous Sun 23 Mar 2014 03:34:00 No.958221 Report

Quoted By:

>>16
I have a fourteen in my crotch, if you know what i mean

Anonymous

18

Anonymous Wed 26 Mar 2014 00:12:00 No.958384 Report

Quoted By:

>>3
Still nowhere close to 'real numbers'
The best you can do is rational numbers + extension fields.

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