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Duck typing is similar to, but distinct from, structural typing.Structural typing is a static typing system that determines type compatibility and equivalence by a type's structure, whereas duck typing is dynamic and determines type compatibility by only that part of a type's structure that is accessed during runtime.
This is sometimes described as "weak typing". For example, Aahz Maruch observes that "Coercion occurs when you have a statically typed language and you use the syntactic features of the language to force the usage of one type as if it were a different type (consider the common use of void* in C). Coercion is usually a symptom of weak typing.
Dynamic polymorphism is more flexible but slower—for example, dynamic polymorphism allows duck typing, and a dynamically linked library may operate on objects without knowing their full type. Static polymorphism typically occurs in ad hoc polymorphism and parametric polymorphism, whereas dynamic polymorphism is usual for subtype polymorphism.
In addition, it avoids the whole class of time-of-check-to-time-of-use (TOCTTOU) vulnerabilities, other race conditions, [28] [30] and is compatible with duck typing. A drawback of EAFP is that it can be used only with statements; an exception cannot be caught in a generator expression, list comprehension, or lambda function.
Structural systems are used to determine if types are equivalent and whether a type is a subtype of another. It contrasts with nominative systems, where comparisons are based on the names of the types or explicit declarations, and duck typing, in which only the part of the structure accessed at runtime is checked for compatibility.
In computer programming, latent typing refers to a type system where types are associated with values and not variables. [1] An example latently typed language is Scheme . This typically requires run-time type checking and so is commonly used synonymously with dynamic typing .
In computer science and logic, a dependent type is a type whose definition depends on a value. It is an overlapping feature of type theory and type systems.In intuitionistic type theory, dependent types are used to encode logic's quantifiers like "for all" and "there exists".
Rewriting the above "hello world!" example to instead be a sequence of two netstrings, itself encoded as a single netstring, gives the following: 17: 5: hello, 6: world!,, Parsing such a nested netstring is an example of duck typing, since the contained string ("5:hello,6:world!,") is both a string and a sequence of netstrings. Its effective ...
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