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In the C family of languages and ALGOL 68, the word cast typically refers to an explicit type conversion (as opposed to an implicit conversion), causing some ambiguity about whether this is a re-interpretation of a bit-pattern or a real data representation conversion. More important is the multitude of ways and rules that apply to what data ...
There are many examples of languages that allow implicit type conversions, but in a type-safe manner. For example, both C++ and C# allow programs to define operators to convert a value from one type to another with well-defined semantics. When a C++ compiler encounters such a conversion, it treats the operation just like a function call.
This behavior exists to avoid integer overflows in implicit narrowing conversions. For example, in the following code: For example, in the following code: In C23 , the boolean type was moved to bool , making the <stdbool.h> header now useless.
For example, in ANSI C: int add_one ( int x ) { int result ; /* declare integer result */ result = x + 1 ; return result ; } The signature of this function definition, int add_one(int x) , declares that add_one is a function that takes one argument, an integer , and returns an integer.
Data typing is static, but weakly enforced; all data has a type, but implicit conversions are possible. User-defined and compound types are possible. Heterogeneous aggregate data types allow related data elements to be accessed and assigned as a unit. The contents of whole structs cannot be compared using a single built-in operator (the ...
For example, suppose that a program defines two types, A and B, where B is a subtype of A. If the program tries to convert a value of type A to type B, which is known as downcasting, then the operation is legal only if the value being converted is actually a value of type B. Thus, a dynamic check is needed to verify that the operation is safe.
The first formal treatments of subtyping were given by John C. Reynolds in 1980 who used category theory to formalize implicit conversions, and Luca Cardelli (1985). [4] The concept of subtyping has gained visibility (and synonymy with polymorphism in some circles) with the mainstream adoption of object-oriented programming.
C++ does not allow the implicit conversion of void* to other pointer types, even in assignments. This was a design decision to avoid careless and even unintended casts, though most compilers only output warnings, not errors, when encountering other casts.