However , mathematicians agree on a particular order of evaluation for several common non-associative operations .
In general , parentheses must be used to indicate the order of evaluation if a non-associative operation appears more than once in an expression .
Mathematicians agree on a particular order of evaluation for several common non-associative operations .
In general , parentheses must be used to indicate the order of evaluation if a non-associative operation appears more than once in an expression .