Brackets ()[]{}
Round Parentheses
Parentheses (round brackets):
- modify the order of execution in APL expressions.
- indicate namelists in function/operator headers.
- surround definitions of namespaces and vectors, from
()(an empty namespace) to definitions that span multiple lines.
A single right parenthesis begins a System Command.
Square Brackets
Square brackets:
- select sub-arrays from an n-dimensional array.
- indicate an axis along which to apply a function.
- surround definitions of arrays of rank 2 or higher; these definitions can span multiple lines.
A single right bracket begins a User Command.
Curly Brackets
Curly brackets:
- indicate shy results and optional left arguments in defined functions.
- enclose the definition of a dfn or a dop.