Direct function

A direct function (dfn, pronounced "dee fun") is an alternative way to define a function and operator (a higher-order function) in the programming language APL. A direct operator can also be called a dop (pronounced "dee op"). They were invented by John Scholes in 1996. They are a unique combination of array programming, higher-order function, and functional programming, and are a major distinguishing advance of early 21st century APL over prior versions. PT← {(+/⍵*2)=2×(⌈/⍵)*2} PT 3 4 51 x 4 5 3 3 11 6 5 13 1217 16 811 12 417 15 8 PT x1 0 1 0 0 1 The factorial function as a dfn:

Direct function

A direct function (dfn, pronounced "dee fun") is an alternative way to define a function and operator (a higher-order function) in the programming language APL. A direct operator can also be called a dop (pronounced "dee op"). They were invented by John Scholes in 1996. They are a unique combination of array programming, higher-order function, and functional programming, and are a major distinguishing advance of early 21st century APL over prior versions. PT← {(+/⍵*2)=2×(⌈/⍵)*2} PT 3 4 51 x 4 5 3 3 11 6 5 13 1217 16 811 12 417 15 8 PT x1 0 1 0 0 1 The factorial function as a dfn: