Variable and Constant Declarations
| variable | constant | type synonym | |
|---|---|---|---|
| ALGOL 68 | modename name «:= initial_value»; | modename name = value; | mode synonym = modename; |
| C (C99) | type name «= initial_value»; | enum{ name = value }; | typedef type synonym; |
| Objective-C | |||
| C++ | const type name = value; | ||
| C# | type name «= initial_value»; or var name = value; |
const type name = value; or readonly type name = value; |
using synonym = type; |
| D | type name «= initial_value»; or auto name = value; |
const type name = value; or immutable type name = value; |
alias type synonym; |
| Java | type name «= initial_value»; | final type name = value; | |
| JavaScript | var name «= initial_value»; | const name = value; | |
| Go | var name type «= initial_value» or name := initial_value |
const name «type» = initial_value | type synonym type |
| Common Lisp | (defparameter name initial_value) or (defvar name initial_value) or (setf (symbol-value 'symbol) initial_value) |
(defconstant name value) | (deftype synonym 'type) |
| Scheme | (define name initial_value) | ||
| ISLISP | (defglobal name initial_value) or (defdynamic name initial_value) |
(defconstant name value) | |
| Pascal | name: type «= initial_value» | name = value | synonym = type |
| Visual Basic | Dim name As type | Const name As type = value | |
| Visual Basic .NET | Dim name As type«= initial_value» | Imports synonym = type | |
| Python | name = initial_value | synonym = type | |
| S-Lang | name = initial_value; | typedef struct {...} typename | |
| Fortran | type name | type, PARAMETER :: name = value | |
| PHP | $name = initial_value; | define("name", value); const name = value (5.3+) |
|
| Perl | «my» $name «= initial_value»; | use constant name => value; | |
| Perl 6 | «my «type»» $name «= initial_value»; | «my «type»» constant name = value; | ::synonym ::= type |
| Ruby | name = initial_value | Name = value | synonym = type |
| Windows PowerShell | «» $name = initial_value | ||
| OCaml | let name «: type ref» = ref value | let name «: type» = value | type synonym = type |
| F# | let mutable name «: type» = value | ||
| Standard ML | val name «: type ref» = ref value | val name «: type» = value | |
| Haskell | «name::type;» name = value | type Synonym = type | |
| Forth | VARIABLE name (in some systems use value VARIABLE name instead) | value CONSTANT name |
^a Pascal has declaration blocks. See Comparison of programming languages (basic instructions)#Functions.
^b Types are just regular objects, so you can just assign them.
^c In Perl, the "my" keyword scopes the variable into the block.
^d Technically, this does not declare name to be a mutable variable—in ML, all names can only be bound once; rather, it declares name to point to a "reference" data structure, which is a simple mutable cell. The data structure can then be read and written to using the ! and := operators, respectively.
Read more about this topic: Comparison Of Programming Languages (basic Instructions)
Famous quotes containing the words variable, constant and/or declarations:
“There is not so variable a thing in nature as a lady’s head-dress.”
—Joseph Addison (1672–1719)
“What, to the American slave, is your Fourth of July? I answer: A day that reveals to him, more than all other days in the year, the gross injustice and cruelty to which he is the constant victim. To him your celebration is a sham.”
—Frederick Douglass (c.1817–1895)
“I judge a man by his actions with men, much more than by his declarations Godwards—When I find him to be envious, carping, spiteful, hating the successes of others, and complaining that the world has never done enough for him, I am apt to doubt whether his humility before God will atone for his want of manliness.”
—Anthony Trollope (1815–1882)