T is a
dialect
A dialect is a Variety (linguistics), variety of language spoken by a particular group of people. This may include dominant and standard language, standardized varieties as well as Vernacular language, vernacular, unwritten, or non-standardize ...
of the
Scheme programming language
A programming language is a system of notation for writing computer programs.
Programming languages are described in terms of their Syntax (programming languages), syntax (form) and semantics (computer science), semantics (meaning), usually def ...
developed in the early 1980s by Jonathan A. Rees,
Kent M. Pitman, and Norman I. Adams of
Yale University
Yale University is a Private university, private Ivy League research university in New Haven, Connecticut, United States. Founded in 1701, Yale is the List of Colonial Colleges, third-oldest institution of higher education in the United Stat ...
as an experiment in language design and implementation.
Rationale
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
BLISS is a system programming language developed at Carnegie Mellon University (CMU) by W. A. Wulf, D. B. Russell, and A. N. Habermann around 1970. It was perhaps the best known system language until C debuted a few years later. Since then, C ...
, which are usually considered to be inherently more efficient than Lisp on conventional machine architectures. Much of this occurs via an
optimizing compiler
An optimizing compiler is a compiler designed to generate code that is optimized in aspects such as minimizing program execution time, memory usage, storage size, and power consumption. Optimization is generally implemented as a sequence of op ...
named Orbit.
T contains some features that modern Scheme lacks. For example, T is
object-oriented
Object-oriented programming (OOP) is a programming paradigm based on the concept of '' objects''. Objects can contain data (called fields, attributes or properties) and have actions they can perform (called procedures or methods and impleme ...
, 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
In programming language theory, lazy evaluation, or call-by-need, is an evaluation strategy which delays the evaluation of an Expression (computer science), expression until its value is needed (non-strict evaluation) and which avoids repeated eva ...
and
flow control, and an equivalent to
Common Lisp
Common Lisp (CL) is a dialect of the Lisp programming language, published in American National Standards Institute (ANSI) standard document ''ANSI INCITS 226-1994 (S2018)'' (formerly ''X3.226-1994 (R1999)''). The Common Lisp HyperSpec, a hyperli ...
'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
In computer programming, ( or ) is a fundamental function in most dialects of the Lisp programming language. ''constructs'' memory objects which hold two values or pointers to two values. These objects are referred to as (cons) cells, conses, ...
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
Inheritance is the practice of receiving private property, titles, debts, entitlements, privileges, rights, and obligations upon the death of an individual. The rules of inheritance differ among societies and have changed over time. Offi ...
.
Ports
T was ported to many hardware
platforms and
operating system
An operating system (OS) is system software that manages computer hardware and software resources, and provides common daemon (computing), services for computer programs.
Time-sharing operating systems scheduler (computing), schedule tasks for ...
s, including:
*
MIPS: DEC 3100 (pmax),
SGI IRIS
*
Motorola 68000
The Motorola 68000 (sometimes shortened to Motorola 68k or m68k and usually pronounced "sixty-eight-thousand") is a 16/32-bit complex instruction set computer (CISC) microprocessor, introduced in 1979 by Motorola Semiconductor Products Sector ...
(m68k): Apollo Domain/OS,
HP/UX, Mac/AUX,
NeXT
NeXT, Inc. (later NeXT Computer, Inc. and NeXT Software, Inc.) was an American technology company headquartered in Redwood City, California that specialized in computer workstations for higher education and business markets, and later develope ...
,
SunOS
SunOS is a Unix-branded operating system developed by Sun Microsystems for their workstation and server computer systems from 1982 until the mid-1990s. The ''SunOS'' name is usually only used to refer to versions 1.0 to 4.1.4, which were based ...
3
*
NS320xx (n32k):
Encore Multimax
*
SPARC: SunOS 4 and above,
Solaris
Solaris is the Latin word for sun.
It may refer to:
Arts and entertainment Literature, television and film
* ''Solaris'' (novel), a 1961 science fiction novel by Stanisław Lem
** ''Solaris'' (1968 film), directed by Boris Nirenburg
** ''Sol ...
,
Unix
Unix (, ; trademarked as UNIX) is a family of multitasking, multi-user computer operating systems that derive from the original AT&T Unix, whose development started in 1969 at the Bell Labs research center by Ken Thompson, Dennis Ritchie, a ...
on
Connection Machine
The Connection Machine (CM) is a member of a series of massively parallel supercomputers sold by Thinking Machines Corporation. The idea for the Connection Machine grew out of doctoral research on alternatives to the traditional von Neumann arch ...
5
*
VAX
VAX (an acronym for virtual address extension) is a series of computers featuring a 32-bit instruction set architecture (ISA) and virtual memory that was developed and sold by Digital Equipment Corporation (DEC) in the late 20th century. The V ...
: Ultrix
See also
References
External links
*
History of T by Olin Shivers
T manual(PDF) from ReadScheme, via the Internet Archive
{{Authority control
Lisp programming language family
Scheme (programming language)
Programming languages created in 1982
Articles with example Lisp (programming language) code