ParadigmMulti-paradigm: object-oriented, imperative, functional, meta
Designed byJonathan A. Rees
Norman I. Adams
DevelopersJonathan A. Rees
Norman I. Adams
First appeared1982; 42 years ago (1982)
Final release
3.0 / August 1, 1984; 39 years ago (1984-08-01)
Typing disciplinedynamic, strong
Influenced by
EuLisp, Joule

T is a dialect of the Scheme programming language developed in the early 1980s by Jonathan A. Rees, Kent M. Pitman, and Norman I. Adams of Yale University as an experiment in language design and implementation.[1]


T's purpose is to test the thesis developed by Guy L. Steele Jr. and Gerald Jay Sussman in their series of papers about Scheme: that Scheme may be used as the basis for a practical programming language of exceptional expressive power, and that implementations of Scheme could perform better than other Lisp systems, and competitively with implementations of programming languages, such as C and BLISS, which are usually considered to be inherently more efficient than Lisp on conventional machine architectures. Much of this occurs via an optimizing compiler named Orbit.

T contains some features that modern Scheme lacks. For example, T is object-oriented, and it has first-class environments, called locales, which can be modified non-locally and used as a module system. T has several extra special forms for lazy evaluation and flow control, and an equivalent to Common Lisp's setf. T, like Scheme, supports call-with-current-continuation (call/cc), but it also has a more limited form called catch. From the T manual, a hypothetical implementation of cons could be:

 (define-predicate pair?)
 (define-settable-operation (car pair))
 (define-settable-operation (cdr pair))
 (define (cons the-car the-cdr)
         (object nil
                 ((pair? self) t)
                 ((car self) the-car)
                 ((cdr self) the-cdr)
                 (((setter car) self new-car) (set the-car new-car))
                 (((setter cdr) self new-cdr) (set the-cdr new-cdr))))

This example shows that objects in T are intimately related to closures and message-passing. A primitive called join puts two objects together, allowing for something resembling inheritance.

1958 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010 2015 2020
 LISP 1, 1.5, LISP 2(abandoned)
 Lisp Machine Lisp
 Scheme  R5RS  R6RS  R7RS small
 ZIL (Zork Implementation Language)
 Franz Lisp
 Common Lisp  ANSI standard
 Le Lisp
 MIT Scheme
 Chez Scheme
 Emacs Lisp
 PLT Scheme  Racket
 GNU Guile
 Visual LISP


T was ported to many hardware platforms and operating systems, including:[2]

See also


  1. ^ Slade, Stephen (1987). The T programming language : a dialect of LISP. Englewood Cliffs, NJ: Prentice-Hall. ISBN 978-0-13-881905-7. OCLC 16094677.
  2. ^ Campbell, Taylor `Riastradh' (7 April 2006). "T Revival Project". Mumble.net. Internet Archive Wayback Machine. Archived from the original on 2007-01-03. Retrieved 2018-11-18.