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While a variable or function may be declared many times, it is typically defined once (in C++, this is known as the One Definition Rule or ODR). Dynamic languages such as JavaScript or Python generally allow functions to be redefined, that is, re-bound; a function is a variable much like any other, with a name and a value (the definition).
Foo.bar(5) print Foo.bar() When executed, should display : 5 Whether or not Foo.bar(5) invokes a function or simply sets an attribute is hidden from the caller. Likewise whether Foo.bar() simply retrieves the value of the attribute, or invokes a function to compute the value returned, is an implementation detail hidden from the caller.
Similarly an array element update is a procedure consisting of three arguments, for example set_array(Array, vector(i,j), value), but many languages also provide syntax such as Array[i,j] = value. A construct in a language is syntactic sugar if it can be removed from the language without any effect on what the language can do: functionality and ...
Variables in standard JavaScript have no type attached, so any value (each value has a type) can be stored in any variable. Starting with ES6, the 6th version of the language, variables could be declared with var for function scoped variables, and let or const which are for block level variables.
The term closure is often used as a synonym for anonymous function, though strictly, an anonymous function is a function literal without a name, while a closure is an instance of a function, a value, whose non-local variables have been bound either to values or to storage locations (depending on the language; see the lexical environment section below).
In Python, functions are first-class objects that can be created and passed around dynamically. Python's limited support for anonymous functions is the lambda construct. An example is the anonymous function which squares its input, called with the argument of 5:
Similarly, the idea of immutable data from functional programming is often included in imperative programming languages, [108] for example the tuple in Python, which is an immutable array, and Object.freeze() in JavaScript. [109]
The specification for pass-by-reference or pass-by-value would be made in the function declaration and/or definition. Parameters appear in procedure definitions; arguments appear in procedure calls. In the function definition f(x) = x*x the variable x is a parameter; in the function call f(2) the value 2 is the argument of the function. Loosely ...