loop to increment a string variable

[Kyle Smith]

I would like to create a file with every combination of letters out to 10 characters.

For example, the first few lines

a
b
c

then eventually

aa
ab
ac

then eventually

aaa
aab
aac

and so on. Finally, it will end with

zzzzzzzzzz


This will create 26^10 lines. Is there a simple way to create a file like this with some kind of loop?

Thanks in advance.

[Jean-Claude Arbaut]

The algorithmic problem of generating these combinations in turn is interesting, but I don't believe you have 1.3 petabyte of RAM to waste for this. For the record, that's the amount of RAM available on the Tianhe-2 supercomputer. So, what are you really trying to do?

Jean-Claude Arbaut

[Nick Cox]

That’s asking for well over a trillion observations. Apart from the memory issue no Stata can oblige at present, I believe. See for your setup

help limits

[daniel klein]

Memory issues aside, see non-documented

mata : strlower(numtobase26((1..100)))

also implemented in Stata as num2base26 (SSC).

Best
Daniel

[William Lisowski]

In thinking about this, I believe the problem is about 4% worse than stated in post #1.

My calculator tells me 26¹⁰ = 141,167,095,653,376, and that is only the number of 10-character strings composed on letters from a 26-letter alphabet.

The total number of strings of length 1 through 10 composed on these letters will be the sum of the geometric series 26 + 26² + ... + 26¹⁰ which is (26/25) * (26¹⁰ - 1) = 146,813,779,479,510.

With apologies to https://youtu.be/QT9BeGNnCqw , you're gonna need a bigger supercomputer.