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Many languages have explicit pointers or references. Reference types differ from these in that the entities they refer to are always accessed via references; for example, whereas in C++ it's possible to have either a std:: string and a std:: string *, where the former is a mutable string and the latter is an explicit pointer to a mutable string (unless it's a null pointer), in Java it is only ...
For a simple type like a number these conventions are relatively clear. Passing ByRef allows the procedure to modify the passed variable whereas passing ByVal does not. For an object, semantics can confuse programmers since an object is always treated as a reference. Passing an object ByVal copies the reference; not the state of the object. The ...
In a programming language, an evaluation strategy is a set of rules for evaluating expressions. [1] The term is often used to refer to the more specific notion of a parameter-passing strategy [2] that defines the kind of value that is passed to the function for each parameter (the binding strategy) [3] and whether to evaluate the parameters of a function call, and if so in what order (the ...
As long as one can access a reference to the data, one can access the data through it, and the data itself need not be moved. They also make sharing of data between different code areas easier; each keeps a reference to it. References can cause significant complexity in a program, partially due to the possibility of dangling and wild references ...
Pointers, references, and pass-by-value are supported for all types (primitive or user-defined). All types (primitive types and reference types) are always passed by value. [4] Memory management can be done manually via new / delete, automatically by scope, or by smart pointers. Supports deterministic destruction of objects.
In computer science, boxing (a.k.a. wrapping) is the transformation of placing a primitive type within an object so that the value can be used as a reference. Unboxing is the reverse transformation of extracting the primitive value from its wrapper object. Autoboxing is the term for automatically applying boxing and/or unboxing transformations ...
Another, more subtle, difference is the role of the semicolon. In Pascal, semicolons separate individual statements within a compound statement; instead in C, they terminate the statement. In C, they are also syntactically part of the statement (transforming an expression into a statement). This difference manifests mainly in two situations:
The "value of a variable" is given by the corresponding mapping in the environment. [2] In languages with assignable variables, it becomes necessary to distinguish between the r-value (or contents) and the l-value (or location) of a variable. [3] In declarative (high-level) languages, values have to be referentially transparent. This means that ...