GLOSSARY.md

Glossary

Glossary of the key terms for functional and object oriented programming. Some additional references:

• Functional programming jargon

• FP glossary

This glossary could also be used as a controlled vocabulary for documentation

Higher-Order Function

A higher-order function (HOF) is:

• A function which takes a function as an argument
• Or a function which returns a function

Motivation:

• Reduce code duplication
• Encourage the single-responsibility principle

More about Higher-Order Function

Currying and closure

These two related concepts in Typescript:

• Closure provides a way of binding a context to a function

• Currying converts a function that takes multiple arguments into a function that takes them one at a time.

• Example: const f = x => y => x + y;

Motivation:

• Make it possible to have function with a single parameter that can be used for .map or .filter while some specific context has been provided before hand

• Make it easier to use Point-Free Style

More about Currying and closure

Purity

A function is pure if the return value is only determined by its parameters

Motivation:

• Make it possible to predict the output based on the input
• Easier to test

More about Purity

Side effects

A function has side effects if the output cannot be predicted just by looking at its input parameters

Motivation:

• Side effects is not desirable from a testing perspective but likely necessary in a real world environment

• Identify side effects to isolate them in a limited number of functions

More about Side effects

Point-Free Style

Point-Free Style allows to chain functions in a very linear way

Motivation:

• Avoid the creation of intermediate variables
• In best cases increases the readability

More about Point-Free Style

Railway oriented programming

Functional approach for composing functions

Motivation:

• Each function will always yield a failure or a success
• Composition of happy paths
• Failure path short-circuits and forwards any previous errors

More about Railway oriented programming

Reactive programming

Declarative programming paradigm concerned with data streams and the propagation of change

Motivation:

• Cleaner code, more concise
• Easier to scale

More about Reactive programming

Functional reactive programming

Programming paradigm for reactive programming using the building blocks of functional programming

Motivation:

• Well defined semantic model
• The dynamical behavior of a value is specified at declaration time
• Stop working on individual events and work with event streams instead

More about Functional reactive programming