Comments on: Generating random strings in Erlang

By: mike

mike — Wed, 01 Jun 2011 15:00:01 +0000

this is my version of random_string:

random_string(0) -> [];
random_string(Length) -> [random_char() | random_string(Length-1)].
random_char() -> random:uniform(95) + 31 .

By: Jed Olivos

Jed Olivos — Mon, 11 Apr 2011 16:29:02 +0000

A big thank you for your article.Much thanks again. Great.

By: teemu

teemu — Sun, 10 Jan 2010 16:27:12 +0000

Hi Zed,

Thanks for the optimization tips. Using tuple for the AllowedChars didn’t come to my mind, but it makes sense performance wise. And your recursive function is definitely more elegant. I have some learning to do with the functional programming still. Still, I wouldn’t say that your example doesn’t need explanation.

By: Zed

Zed — Wed, 06 Jan 2010 21:56:16 +0000

Just for some premature optimization hints
- you are evaluating the length of AllowedChars in each call of your folded function, which is an o(N) operation.
- you could be using an AllowedChars tuple. Accessing the n-th element of a list is o(N), while o(1) for an tuple.

Also instead of the obscure folding you could just create a recursive function for building the list. For example:

random_str(0, _Chars) -> [];
random_str(Len, Chars) -> [random_char(Chars)|random_str(Len-1, Chars)].
random_char(Chars) -> element(random:uniform(tuple_size(Chars)), Chars).

This would render your statement of “Erlang is not the most readable language” pointless, as the code is so readable, it doesn’t even need an explanation