A variation of lambda notation for specifying functions using numbers instead of names to refer to {formal parameters}. A reference to a formal parameter is a number which gives the number of lambdas (written as here) between the reference and the lambda which binds the parameter. E.g. the function f . x . f x would be written . . 1 0. The 0 refers to the innermost lambda, the 1 to the next etc. The chief advantage of this notation is that it avoids the possibility of name capture and removes the need for {alpha conversion}. [N.G. De Bruijn, "Lambda Calculus Notation with Nameless Dummies: A Tool for Automatic Formula Manipulation, with Application to the Church-Rosser Theorem", Indag Math. 34, pp 381-392]. (2003-06-15)
