Scala2e Chapter5 Basic Types and Operations 5.8 Operator precedence and associativity

Operator precedence determines which parts of an expression are evaluated before the other parts.

show the precedence given to the first character of a method in decreasing order of precedence, with characters on the same line having the same precedence.
The higher a character is in this table, the higher the precedence of methods that start with that start with that character.

Any method that ends in a ':' character is invoked on its right operand, passing in the left operand.
Methods that end in any other character are the other way around.
They are invoked on their left operand, passing in the right operand.
So a * b yields a.*(b), but a ::: b yields b. :::(a).