Assignments

Mathematica's symbolic architecture supports a highly generalized notion of assignment, in which you can specify a transformation for any class of expressions defined by a Mathematica pattern. Simple cases correspond to assignments for "variables", "indexed variables" or "structure elements". Other cases define functions or general transformations.

x = v — assign a value (Set )

{ x , y } = { u , v } — assign multiple values

{ x , y } = { y , x } — swap values

a [ [ i ] ] = v — assign a value to a list/array/expression element

x++ (Increment )  ▪ ++ x (PreIncrement )  ▪ x+= y (AddTo )

x-- (Decrement )  ▪ -- x (PreDecrement )  ▪ x-= y (SubtractFrom )

x*= y (TimesBy )  ▪ x/= y (DivideBy )

AppendTo , PrependTo — add elements to a list

Function Definitions

f [ x _ ] := body — define a function

Forms of Assignment

lhs = rhs — immediate assignment, with rhs evaluated at the time of assignment

lhs := rhs — delayed assignment, with rhs reevaluated every time it is used

f /: lhs = rhs , f /: lhs := rhs — associate assignments with the head f

lhs ^= rhs , lhs ^:= rhs — define "upvalues" associated with the leading head in lhs

Clearing Assignments

x =. — unset the value of x (Unset )

Clear — clear all values associated with a symbol

ClearAll   ▪ Remove

Information about Assignments

? x (Information ) — get information about all assignments for x

DownValues   ▪ UpValues   ▪ Save

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