# Talk:Count in factors

## task note[edit]

It'd be best to include the "factor" function, and note where it came from. --Michael Mol 21:23, 23 December 2010 (UTC)

## Draft/Non-draft[edit]

While I don't see any problems, or have any complaints with peoples' implementations, I want to hold off until Jan 1st before un-drafting; there are a few languages and participants I usually see, but I don't see their solutions yet. --Michael Mol 18:17, 24 December 2010 (UTC)

- What can I say? Christmas is when good food and drink take precedence over coding… –Donal Fellows 21:00, 24 December 2010 (UTC)
- Hey, I'm not complaining! Enjoy the holidays! :) --Michael Mol 21:20, 24 December 2010 (UTC)

Perhaps rather than having a special rule for 1, the count should start from 2? --Rdm 19:16, 27 December 2010 (UTC)

- It'd make it neater, algorithmically, but then it defies the simplistic concept of counting. I could rationalize, too, that having the troublesome case of -is-not-prime, is normal for the problem at hand, and helps expose workarounds and idiomatic approaches for special cases. Really, though, it comes down to the fact that when I count to ten, I start at one. --Michael Mol 20:02, 27 December 2010 (UTC)
- Ok, well.. technically speaking, the list of prime factors for 1 is the empty list. But I suppose representing that might look odd to some people. --Rdm 23:58, 27 December 2010 (UTC)

## duplicate task?[edit]

What's different to just calling Prime decomposition in a loop? Is this really worth a separate task? --Oenone 09:09, 19 April 2011 (UTC)

- It's not a duplicate, because it's an extension of the behavior of another task, and serves its own purpose (that of showing the factors of a sequence of numbers) --Michael Mol 12:21, 19 April 2011 (UTC)

## phantom categories - incorrect use of Library templates[edit]

I found this looking into category cleanup. Library templates (D, Ruby) for modules by name Prime, UIprime create categories. I would expect the library template would address the name of a general library and then reference a specific member. This usage is creating clutter all over RC.

- Knowledgeable Ruby and D users - help please.

--Dgamey 11:40, 18 May 2011 (UTC)

- (With Ruby) 'prime' is a library, and its members are Prime, Prime#prime_division, Integer#prime_division, Prime::Generator23 and so on. The 'prime' library is part of the standard library. I am not wanting phantom categories for libraries of the standard library ('prime', 'optparse', 'strscan', 'find', 'securerandom' and so on), so I am removing them. --Kernigh 16:45, 22 August 2011 (UTC)

## stating that 1 is prime[edit]

I marked Python as *partly incorrect* (which was later rescinded) that Python marked **1** as a prime, not that **1** was included in the listing (with **1** as a factor). It was the *marking* of **1** as a prime that was indicated as (partly) incorrect. Other than that, the factors of the integers listed were correct. Nowhere did I indicate that **1** shouldn't be in the list. I don't know any other method of flagging an entry to address this situation of ancillary output being incorrect. -- Gerard Schildberger (talk) 20:56, 27 October 2013 (UTC)

- I've changed it. 1 is "not composite" but that would mess with the formatting. --Paddy3118 (talk) 21:07, 27 October 2013 (UTC)

- Yes, thank for correcting the program. I had misgivings about flagging it, but it was a very simple change to correct the error, even though it wasn't part of the task's requirements. (I always appreciate programmers that go the
*extra mile*, even if it's just a few steps.) I think adding a prime counter to various programs would verify that the program works correctly, at least in factoring composites. I'm in the process of adding aforementioned code to the REXX program, with proper handling of unity. -- Gerard Schildberger (talk)

- Yes, thank for correcting the program. I had misgivings about flagging it, but it was a very simple change to correct the error, even though it wasn't part of the task's requirements. (I always appreciate programmers that go the

## 1 is a prime ...[edit]

**1** *is* a prime ... or rather, it was at one time.

The Classical Greeks thought that, and G. H. Hardy was one of last mathematicians to believe that **1** was prime.

It was sometime in the 1930's that unity was "officially" declared to not be a prime; in 1938, Hardy
updated (his) definition of a *prime* (in his book, *A Course in Pure Mathematics*), and also
stated that **2** is the smallest prime.

For further reading, see the blog why isn't 1 a prime number at the *Scientific American* site. -- Gerard Schildberger (talk) 01:32, 28 June 2020 (UTC)