pointervalued

Pointer-valued is a term used in programming to describe types or values that represent memory addresses rather than direct values. A pointer-valued value stores an address; by dereferencing it, the program accesses the object located at that address. In languages that distinguish value types from reference or pointer types, pointer-valued values enable indirect access and sharing, as multiple pointers may refer to the same object.

Operations on pointer-valued values typically include assignment by copying the pointer, dereferencing to obtain or modify the pointed-to object, and, in languages that permit pointer arithmetic, arithmetic on the address. They may also include a special null or nil value representing a non-pointing address. Managing the lifetime of the referent is important to avoid dangling pointers or memory leaks.

In practice, pointer-valued types are used to implement dynamic data structures (linked lists, trees), to pass large objects efficiently, and to interface with low-level system or hardware facilities. Different languages treat pointers and pointer-valued types differently:

- In C and C++, pointers are explicit and support pointer arithmetic; raw pointers can be null or dangling, requiring careful memory management.

- In Rust, raw pointers (*const T, *mut T) are pointer-valued but unsafe to dereference; references (&T, &mut T) are safe, non-pointer-valued abstractions.

- In Go, pointers are values of pointer-valued types like *T, with automatic garbage collection and restrictions on arithmetic.

Pointer-valued is sometimes contrasted with value types, where the value itself is stored and copying it duplicates the data. The term appears in API documentation and language specifications to indicate that a parameter, return type, or field holds an address rather than a concrete object.