The Wolfram Language'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 Wolfram Language 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

AssociateTo , KeyDropFrom — modify an association

x//= f (ApplyTo ) — x=f[x]

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   ▪ OwnValues   ▪ UpValues   ▪ SubValues   ▪ DefaultValues   ▪ ValueQ   ▪ Save