conversion

n 1: an event that results in a transformation [syn: {transition},

{changeover}]

2: a change in the units or form of an expression: "conversion

from Fahrenheit to Centigrade

3: a score in American football made on a try for points after

a touchdown [syn: {point after}, {extra points}]

4: a spiritual enlightenment causing a person to lead a new

life [syn: {rebirth}, {spiritual rebirth}]

5: a defense mechanism represses emotional conflicts which are

then converted into physical symptoms that have no organic

basis

6: interchange of subject and predicate of a proposition

7: act of exchanging one type of money or security for another

8: the act of changing from one use or function or purpose to

another

eta conversion

In {lambda-calculus}, the eta conversion rule states

\ x . f x <--> f

provided x does not occur as a {free variable} in f and f is a

function. Left to right is eta reduction, right to left is

eta abstraction (or eta expansion).

This conversion is only valid if {bottom} and \ x . bottom are

equivalent in all contexts. They are certainly equivalent

when applied to some argument - they both fail to terminate.

If we are allowed to force the evaluation of an expression in

any other way, e.g. using {seq} in {Miranda} or returning a

function as the overall result of a program, then bottom and

\ x . bottom will not be equivalent.

See also {observational equivalence}, {reduction}.