Elvis operator

[Alex Buckley]

Dierk,

Thank you very much for writing.

Putting ?: and ?. side-by-side shows they are dual in a type-theoretic 
sense. ?: returns a specific value of a specific type (indicating a 
default), while ?. returns a non-value of the bottom type. Since the 
bottom type is a subtype of all other types, the non-value will swallow 
all messages sent to it. The non-value turns into the null reference at 
assignment conversion or method invocation conversion, of course.

Turning to more practical matters, do you have a sense of how often ?. 
is used in Groovy code? Why would anyone dereference with '.' when they 
could use '?.' ? If '.' is still commonly used, is Groovy code littered 
with as many == comparisons with null as Java code is?

Alex