Parentheses are used to define tuples and to apply functions. For functions with a single argument, parentheses are optional. In these cases you may need to use

Parentheses are used to define tuples and to apply functions. For functions with a single argument, parentheses are optional. In these cases you may need to use braces to enclose some expression. Example: 1 to 10 filter (_%2==0) The parentheses in this case are optional, but if you omit them you´ll have to put expression _%2==0 inside a pair of braces: 1 to 10 filter {_%2==0}