Hi,

2011/1/18 Martin Asser Hansen <mail / maasha.dk>:
> I was wondering why Ruby don't have a low level implementation of bitwise
> operators for strings.

You may know, Integer has bitwise operators.

We know that we need binary/bitwise methods/operators for strings,
and add String#getbyte/setbyte before, but we didn't have enough
use cases and knowledge about them.

So if you provide enough use cases, we can design and implement.

> This is extremely useful for detecting changes in
> strings such as Hamming Distance - which in Perl is super efficient:
> sub hamming_distance($$)
> {
> length( $_[ 0 ] ) - ( ( $_[ 0 ] ^ $_[ 1 ] ) =~ tr[\0][\0] )
> }
> The optimal implementation would perform bitwise operations on machine words
> at a time (i.e. 32 or 64 bits).
> This feature is also useful for bitarrays.

There was a proposal of String#hamming_distance.
http://redmine.ruby-lang.org/issues/show/2571
But it was rejected because
* String#hamming_distance doesn't have enough use cases to implement as builtin.
* People may want to have String#levenshtein distance if it is merged
* it should be extension library or provided as gem.

The patch also provided String#^ but it was also rejected because
String#^'s behavior is not clear
* bitwise or binary?
* when the length or two strings are different

Anyway I agree with the needs of bitwise methods.
If you have a comprehensive proposal with enough use cases, we can
begin the discussion.

-- 
NARUSE, Yui naruse / airemix.jp>