Another ruby funny that caught me out... Want to guess what these should output?

not_matches_vs_does_not_match.rb

"fish" =~ /ish/ 

"fish" !=~ /ish/

!("fish" =~ /ish/)  # equivalent to "fish" !~ /ish/ - thanks @MrJaba and @kerryb!

Note: If anyone has a link that explains what line 3 is doing, I would appreciate it. I'm sure I once knew, but it certainly is not intuitive.

(sorry, meant to say second example, which happens to have the line number 3 - just to avoid more confuddlementz)

Aren't you looking for "fish" !~ /ish/ ? I'm not sure what !=~ does.

Good catch, exactly the same time as Tom! But I'm super-curious as to what !=~ does... it gives a result, just it always seems to be true!

The answer, with props to @MrJaba, is that the syntax actually splits up like this:

"fish"   !=    ~/ish/

So it applies the unary one's compliment operator to a regexp before doing an inequality test. The ~ operator, for those who don't know, does this:

~1  #=> -2  - turning binary 0000 0001 into 1111 1110
~42 #=> -43 - turning binary 0010 1010 into 1101 0101 

This is undefined for string, and even boolean, but for regex it is defined as nil. No idea why.

So the only way of getting a false with a regex would be:

nil !=~ /anything goes here/

Anything non-nil will always return true, thanks to the !=