About ATS

What is ATS?

ATS is a statically typed programming language that unifies implementation with formal specification. It is equipped with a highly expressive type system rooted in the framework Applied Type System, which gives the language its name. In particular, both dependent types and linear types are available in ATS.

The current implementation of ATS2 (ATS/Postiats) is written in ATS1 (ATS/Anairiats). ATS can be as efficient as C/C++ both time-wise and memory-wise (see The Computer Language Benchmarks Game for concrete evidence) and supports a variety of programming paradigms that include:

  • Functional programming. The core of ATS is a functional language based on eager (aka. call-by-value) evaluation, which can also accommodate lazy (aka. call-by-need) evaluation. The availability of linear types in ATS often makes functional programs written in it run not only with surprisingly high efficiency (when compared to C) but also with surprisingly small (memory) footprint (when compared to C as well).

  • Imperative programming. The novel and unique approach to imperative programming in ATS is firmly rooted in the paradigm of programming with theorem-proving. The type system of ATS allows many features considered dangerous in other languages (e.g., explicit pointer arithmetic and explicit memory allocation/deallocation) to be safely supported in ATS, making ATS a viable programming language for low-level systems programming.

  • Concurrent programming. ATS, equipped with a multicore-safe implementation of garbage collection, can support multithreaded programming through the use of pthreads. The availability of linear types for tracking and safely manipulating resources provides an effective means to constructing reliable programs that can take advantage of multicore architectures.

  • Modular programming. The module system of ATS is largely infuenced by that of Modula-3, which is both simple and general as well as effective in supporting large scale programming.

In addition, ATS contains a subsystem ATS/LF that supports a form of (interactive) theorem-proving, where proofs are constructed as total functions. With this component, ATS advocates a programmer-centric approach to program verification that combines programming with theorem-proving in a syntactically intertwined manner. Furthermore, this component can serve as a logical framework for encoding deduction systems and their (meta-)properties.

What is ATS good for?

  • ATS can enforce great precision in practical programming.

  • ATS allows the programmer to write efficient functional programs that directly manipulate native unboxed data representation.

  • ATS allows the programmer to reduce the memory footprint of a program by making use of linear types.

  • ATS allows the programmer to enhance the safety (and efficiency) of a program by making use of theorem-proving.

  • ATS allows the programmer to write safe low-level code that runs in OS kernels.

  • ATS can help teach type theory, demonstrating concretely the power and potential of types in constructing high-quality software.


The development of ATS has been funded in part by National Science Foundation (NSF) under the grants no. CCR-0081316/CCR-0224244, no. CCR-0092703/0229480, no. CNS-0202067, no. CCF-0702665 and no CCF-1018601. As always, any opinions, findings, and conclusions or recommendations expressed here are those of the author(s) and do not necessarily reflect the views of the NSF.

This page is created with ATS by Hongwei Xi and also maintained by Hongwei Xi. SourceForge.net Logo