In
lambda calculus,
Lisp,
scheme, and
haskell, lambda is used
to create an
abstraction---that is, an unnamed function. For
example, the function which computes the square of its argument
may be written as:
\lambda x . * x x (in lambda calculus, assuming * has been
defined)
(lambda (x) (* x x)) (in Lisp and scheme)
\ x -> (x * x) (in haskell).
In
ML, lambda is called `
fn':
fn x => (x * x)