Component Pascal vs. Crystal vs. Haskell vs. test_coverage Comparison Chart

Component Pascal is a general-purpose language in the tradition of Pascal, Modula-2, and Oberon. Its most important features are block structure, modularity, separate compilation, static typing with strong type checking (also across module boundaries), type extension with methods, dynamic loading of modules, and garbage collection. Type extension makes Component Pascal an object-oriented language. An object is a variable of an abstract data type consisting of private data (its state) and procedures that operate on this data. Abstract data types are declared as extensible records. Component Pascal covers most terms of object-oriented languages by the established vocabulary of imperative languages in order to minimize the number of notions for similar concepts. Complete type safety and the requirement of a dynamic object model make Component Pascal a component-oriented language.

Every expression in Haskell has a type that is determined at compile time. All the types composed together by function application have to match up. If they don't, the program will be rejected by the compiler. Types become not only a form of guarantee, but a language for expressing the construction of programs. Every function in Haskell is a function in the mathematical sense (i.e., "pure"). Even side-effecting IO operations are but a description of what to do, produced by pure code. There are no statements or instructions, only expressions that cannot mutate variables (local or global) nor access state like time or random numbers. You don't have to explicitly write out every type in a Haskell program. Types will be inferred by unifying every type bidirectionally. However, you can write out types if you choose, or ask the compiler to write them for you for handy documentation.