问题
I have an associative operation >>. The problem is that its cost linearly depends on the size of its left operand. So an expression formed by a sequence of n applications of >> like
a >> a >> a >> a >> a >> ... >> a
it has quadratic cost in terms of n, because by default infix operators are left-associative. How to make it right-associative so that the cost of such an expression is kept linear in terms of n?
回答1:
I found a solution. Scala reference says in section 6.12.3 Infix Operations:
The associativity of an operator is determined by the operator’s last character. Operators ending in a colon ‘:’ are right-associative. All other operators are left-associative.
Therefore it was enough to rename >> to >>:.
It took me some time to realize that while a >> b is desugared into a.>>(b), a >>: b is desugared into b.>>:(a). So I had to define >>: as
def >>:(x: T): T = x >> this
来源：https://stackoverflow.com/questions/15384744/how-to-make-a-right-associative-infix-operator