Agda is a dependently typed functional programming language based on intuitionistic Type Theory. Type theory is concerned both with programming and logic.
It’s an extension of Martin-Löf’s type theory, and is the latest in the tradition of languages developed in the programming logic group at Chalmers. It has inductive families, i.e., data types which depend on values, such as the type of vectors of a given length. It also has parametrized modules, mixfix operators, Unicode characters, and an interactive Emacs interface which can assist the programmer in writing the program. Other languages in this tradition are Alf, Alfa, Agda 1, Cayenne. Some other loosely related languages are Coq, Epigram, and Idris.
Agda is also a proof assistant based on the propositions-as-types paradigm, but has no separate tactics language, and proofs are written in a functional programming style.
Agda is open-source and enjoys contributions from many authors. The center of the Agda development is the Programming Logic group at Chalmers and Gothenburg University.
Here’s our recommended free books to learn about Agda and Type Theory.
1. Programming Languages Foundations in Agda by Philip Wadler with contributions from Wen Kokke, Jeremy Siek
Programming Languages Foundations in Agda is an introduction to programming language theory using the proof assistant Agda.
This book offers good coverage of logical foundations and programming language foundations. The book is broken into two parts. The first part, Logical Foundations, develops the needed formalisms. The second part, Programming Language Foundations, introduces basic methods of operational semantics.
Programming Languages Foundations in Agda is licensed under a Creative Commons Attribution 4.0 International License.
2. Agda User Manual by The Agda Team
This is the manual for the Agda programming language, its type checking, compilation and editing system and related resources/tools.
A detailed description of the Agda language is given in the Language Reference chapter looking at built-ins, coinduction, copatterns, data types, function types, lambda abstraction, module system, postulates, prop, and much more.
Guidance on how the Agda editing and compilation system can be used can be found in the Tools chapter.
3. Programming in Martin-Löf’s Type Theory by Bengt Nordström, Kent Petersson, Jan M. Smith
Programming in Martin-Löf’s Type Theory describes different type theories (theories of types, polymorphic and monomorphic sets, and subsets) from a computing science perspective.
It’s intended for researchers and graduate students with an interest in the foundations of computing science, and it’s mathematically self-contained.
This book was published by Oxford University Press in 1990. It is now out of print.
4. Towards a practical programming language based on dependent type theory by Ulf Norell
This thesis is concerned with bridging the gap between the theoretical presentations of type theory and the requirements on a practical programming language.
The author presents a type checking algorithm for a theory with metavariables and prove its soundness independent of whether the metavariables are solved or not.
The thesis ends with the implementation of a programming language, Agda, based on type theory. As an illustrating example, the author shows how to program a simple certified prover for equations in a commutative monoid, which can be used internally in Agda.
All books in this series:
Free Programming Books | |
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