updates

20200807173133-decentralized_social_networks.org

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+#+title: Decentralized social networks
+* Secure Scuttlebutt (SSB)
+- https://en.wikipedia.org/wiki/Secure_Scuttlebutt
+- https://scuttlebutt.nz/
+- https://www.manyver.se/
+- https://github.com/fraction/oasis
+
+  How do these differ from services like Diaspora or Mastodon?

20201007142751-python_typing.org

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+#+title: Python Typing
+
+Python does not require nor enforce strict typing, and instead takes a dynamic
+approach using [[file:20201008164244-duck_typing.org][Duck Typing]].
+
+Optional [[file:20201008164835-structural_typing.org][Structural Typing]] support for Python is provided via type hints as
+described in [[https://www.python.org/dev/peps/pep-0484/][PEP-484]].
+
+Variables, function arguments, and return values can have their types annotated,
+e.g. "variable x has type integer" or "function y takes a string and returns a
+list of dictionaries". While these are optional and not checked at run-time,
+they serve as documentation and can be used by various type checkers to ensure
+program correctness.
+
+* Available Type Checkers
+- Mypy :: http://mypy-lang.org/
+- Pyright (Microsoft) :: https://github.com/Microsoft/pyright
+- Pyre (Facebook) :: https://pyre-check.org/
+- Pytype (Google) :: https://google.github.io/pytype/
+
+* Limitations
+- Type hints do not guarantee purity.
+- Type hints are not checked at run-time.
+* Fun facts
+- Python's =boolean= inherits from =int=, hence =True + True = 2=.

20201008164244-duck_typing.org

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+#+title: Duck Typing
+
+#+begin_quote
+Duck typing in computer programming is an application of the duck test—"If it
+walks like a duck and it quacks like a duck, then it must be a duck"—to
+determine if an object can be used for a particular purpose. With normal typing,
+suitability is determined by an object's type. In duck typing, an object's
+suitability is determined by the presence of certain methods and properties,
+rather than the type of the object itself.
+
+--- https://en.wikipedia.org/wiki/Duck_typing
+#+end_quote
+
+This contrasts with [[file:20201008164835-structural_typing.org][Structural Typing]], where the type of the object itself is
+used to determine its suitability.

20201008164835-structural_typing.org

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+#+title: Structural Typing
+
+#+begin_quote
+A structural type system (or property-based type system) is a major class of
+[[file:20201008164956-type_system.org][Type System]] in which type compatibility and equivalence are determined by the
+type's actual structure or definition and not by other characteristics such as
+its name or place of declaration. Structural systems are used to determine if
+types are equivalent and whether a type is a subtype of another.
+
+--- https://en.wikipedia.org/wiki/Structural_type_system
+#+end_quote
+
+* Benefits
+** Easier reasoning
+Types make it easier to reason about code, as they describe succinctly what a
+function can do. If a function takes a single string as an argument and returns an integer, there's only so many things
+** Error reduction
+While types are not a substitute for testing, they do obviate a class of tests
+that you have to write yourself.

20201008164956-type_system.org

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+#+title: Type System
+
+Used in [[file:20200723095845-software_development.org][Software Development]].
+
+#+begin_quote
+In programming languages, a type system is a logical system comprising a set of
+rules that assigns a property called a type to the various constructs of a
+computer program, such as variables, expressions, functions or modules.
+
+--- https://en.wikipedia.org/wiki/Type_system
+#+end_quote