subtraction

n 1: an arithmetic operation in which the difference between two

numbers is calculated; "the subtraction of three from

four leaves one"; "four minus three equals one" [syn: {minus}]

2: the act of subtracting (removing a part from the whole); "he

complained about the subtraction of money from their

paychecks" [syn: {deduction}] [ant: {addition}]

abstraction

1. Generalisation; ignoring or hiding details to capture some

kind of commonality between different instances. Examples are

{abstract data types} (the representation details are hidden),

{abstract syntax} (the details of the {concrete syntax} are

ignored), {abstract interpretation} (details are ignored to

analyse specific properties).

2. Parameterisation, making something a function

of something else. Examples are {lambda abstractions} (making

a term into a function of some variable), {higher-order

function}s (parameters are functions), {bracket abstraction}

(making a term into a function of a variable).

Opposite of {concretisation}.

(1998-06-04)