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Call by reference can therefore be used to provide an additional channel of communication between the called function and the calling function.

A call-by-reference language makes it more difficult for a programmer to track the effects of a function call, and may introduce subtle bugs.

However, the term "call by sharing" is not in common use; the terminology is inconsistent across different sources.

For example, in the Java community, they say that Java is call by value.

In purely functional languages there is typically no semantic difference between the two strategies (since their data structures are immutable, so there is no possibility for a function to modify any of its arguments), so they are typically described as call by value even though implementations frequently use call by reference internally for the efficiency benefits.

Following is an example that demonstrates call by reference in E: Java (for object references), Ruby, Java Script, Scheme, OCaml, Apple Script, and many others.

Evaluation strategies are used by programming languages to determine when to evaluate the argument(s) of a function call (for function, also read: operation, method, or relation) and what kind of value to pass to the function.

For example, call by value/call by reference specifies that a function application evaluates the argument before it proceeds to the evaluation of the function's body and that it passes two capabilities to the function, namely, the ability to look up the current value of the argument and to modify it via an assignment statement. Some languages, especially lower-level languages such as C , combine several notions of parameter passing.

The description "call by value where the value is a reference" is common (but should not be understood as being call by reference); another term is call by sharing.

Thus the behaviour of call by value Java or Visual Basic and call by value C or Pascal are significantly different: in C or Pascal, calling a function with a large structure as an argument will cause the entire structure to be copied (except if it's actually a reference to a structure), potentially causing serious performance degradation, and mutations to the structure are invisible to the caller.

Purely functional languages like Haskell, as well as non-purely functional languages like R, use call by need.

The evaluation strategy is specified by the programming language definition, and is not a function of any specific implementation.

Many languages support call by reference in some form or another, but comparatively few use it as a default.

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