Type systems

• strong vs. weak

  • not consistently defined

  • 1+"1". strong: fails, weak: something happens (coercion); 1+1.0 is more subtle

• static vs. dynamic

  • types are known without running the code (usually at compile time) and can't change

  • C++, C, Haskell vs. Python, JavaScript

• manifest vs. inferred

  • you manually declare the type vs. the compiler figures it out

  • C++, Rust vs. Python, Rust, Haskell

• nominal vs. structural

  • compatibility is determined based on name (int) vs. structure (can add 1 to it)

  • C++ vs. Haskell, Python, Mathematica (to some extent)