# Talk:Operator precedence

From Rosetta Code

## maybe a little more specific?[edit]

What does "associate from left to right" mean?

When I look at

- ((a + b) + c)

or

- (a + (b + c))

I could implement either of them by associating from left to right. In the first case, I would be doing bottom-up association, in the second case I would be doing top-down association. --Rdm 18:20, 24 September 2012 (UTC)

- From here, given the expression without parenthesis of a + b + c then if '+' is left associative it should be evaluated as (a + b) + c, which I think is what was meant by "associate from left to right". You can add brackets to make the evaluation order explicit, the associativity is used when you don't. --Paddy3118 20:12, 24 September 2012 (UTC)

- In the specific case of
`+`as applied to integers (either of unlimited precision or in the finite 2s-complement groups as usually implemented by modern hardware) the associativity doesn't matter too much as the operation is also properly commutative. Where it*does*matter is with operators like division, exponentiation or list-prepending. (It also matters with addition of floating point numbers, but for more subtle reasons.) –Donal Fellows 07:55, 27 September 2012 (UTC)

- In the specific case of