valtyper

Valtyper are a concept in programming that describes data types whose values are stored directly in variables rather than as references to heap-allocated objects. In languages that distinguish value types from reference types, valtyper exhibit value semantics: assigning one variable to another copies the entire value, and changes to one variable do not affect others. They typically have a deterministic memory layout and do not require dereferencing to access their contents, which can improve locality and performance.

Common examples of valtyper include primitive numbers (integers, floating-point numbers), booleans, and character types. Many languages also allow user-defined value types, such as structs or tuples, depending on their type system. The handling of nullability varies: some languages treat value types as non-nullable by default, while others provide nullable wrappers or optional types.

In contrast, reference types store references to objects allocated on the heap, and copying a reference shares the same underlying object. This distinction affects memory management, garbage collection, and equality semantics, with value types often using content-based equality unless overridden.

Language-specific notes: in C#, value types include primitives and the struct type; they can be boxed to be treated as objects, introducing heap allocation and a performance cost. In C++, value semantics are the default for most types, with explicit support for move semantics and manual memory management. In many modern languages, value types are designed to be lightweight and efficiently copied, while complex or large data structures may be modeled as reference types to avoid costly copying.

See also: reference type, boxing, value semantics.