These commands test expr for various forms of function composition.

The type(expr, `@`) calling sequence returns true if expr is a composition of functions.  It is equivalent to type(expr, specfunc(anything, `@`)).

The type(expr, `@@`) calling sequence returns true if expr is a repeated composition.  It is equivalent to type(expr, specfunc(anything, `@@`)).

The type(expr, composition) calling sequence returns true if expr is either of type @ or @@.

For more information about function composition, see compose.