EuLisp

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EuLisp
EuLispLogo.png
Paradigmmulti-paradigm: functional, procedural, meta, object-oriented
FamilyLisp
First appeared1990; 34 years ago (1990)
Preview release
0.991[1] / 2010; 14 years ago (2010)
Typing disciplinestrong, dynamic
Scopestatic and dynamic
OSLinux
Filename extensions.em
Major implementations
EuXLisp,[2] Youtoo,[2] Eu2C[2]
Influenced by
Common Lisp, InterLisp, LeLisp, Lisp/VM, Scheme, T, CLOS, ObjVlisp, Oaklisp, MicroCeyx, MCS, Standard ML, Haskell
Influenced
Dylan, ISLISP, Evelin

EuLisp is a statically and dynamically scoped Lisp dialect developed by a loose formation of industrial and academic Lisp users and developers from around Europe. The standardizers intended to create a new Lisp "less encumbered by the past" (compared to Common Lisp), and not so minimalist as Scheme. Another objective was to integrate the object-oriented programming paradigm well. It is a third-generation programming language.

Origin

The language definition process first began in a meeting in 1985 in Paris and took several years. The complete specification and a first implementation (interpreted-only) were made available in 1990.

Timeline of Lisp dialects(edit)
1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010 2015 2019
 LISP 1, 1.5, LISP 2(abandoned)
 Maclisp
 Interlisp
 Lisp Machine Lisp
 Scheme  R5RS  R6RS  R7RS small
 NIL
 Franz Lisp
 Common Lisp
 Le Lisp
 T
 Emacs Lisp
 AutoLISP
 OpenLisp
 PicoLisp
 EuLisp
 ISLISP
 newLISP
 Racket
 GNU Guile
 Visual LISP
 Qi, QiII  Shen
 Clojure
 Arc
 LFE
 Hy

Distinguishing features

Its main traits are that it is a Lisp-1 (no separate function and variable namespaces), has a Common Lisp Object System (CLOS) style generic-function type object-oriented system named The EuLisp Object System (TELOS) integrated from the ground up, has a built-in module system, and is defined in layers to promote the use of the Lisp on small, embedded hardware and educational machines. It supports continuations, though not as powerfully as Scheme. It has a simple lightweight process mechanism (threads).

Summary

  • A definition in levels, currently Level-0 and Level-1
  • Modules based on (non-first-class) lexical environments.
  • Lexically scoped, with dynamic or late binding available in Level-1.
  • A single name space for function and variable names (like Scheme).
  • Lightweight processes.
  • A fully integrated object system with single inheritance at Level-0 and multiple inheritance and meta-object protocol at Level-1.
  • An object-oriented condition system.

Implementations

An early implementation of EuLisp was Free and Eventually Eulisp (FEEL). The successor to FEEL was Youtoo (interpreted and compiled versions), by University of Bath in the United Kingdom .[3] An interpreter for the basic level of EuLisp, level-0, was written by Russell Bradford in XScheme, an implementation of Scheme by David Michael Betz, originally named EuScheme EuScheme but the most recent version is renamed EuXLisp [1] to avoid confusion. Also Eu2C [2], a EuLisp optimizing compiler, was created by Fraunhofer ISST under the APPLY project in Germany [3].

A dialect of EuLisp was developed, named Plural EuLisp. It was EuLisp with parallel computing programming extensions.

Example

Example use of classes in the algorithm to solve the "Towers of Hanoi" problem. 

(defmodule hanoi
  (syntax (syntax-0)
   import (level-0)
   export (hanoi))

;;;-------------------------------------------------
;;; Tower definition
;;;-------------------------------------------------
(defconstant *max-tower-height* 10)

(defclass <tower> ()
  ((id reader: tower-id keyword: id:)
   (blocks accessor: tower-blocks)))

(defun build-tower (x n)
  (labels ((loop (i res)
                 (if (= i 0) res
                   (loop (- i 1) (cons i res)))))
          ((setter tower-blocks) x (loop n ()))
          x))

(defmethod generic-print ((x <tower>) (s <stream>))
  (sformat s "#<tower ~a: ~a>" (tower-id x) (tower-blocks x)))

;;;-------------------------------------------------
;;; Access to tower blocks
;;;-------------------------------------------------
(defgeneric push (x y))

(defmethod push ((x <tower>) (y <fpi>))
  (let ((blocks (tower-blocks x)))
    (if (or (null? blocks) (< y (car blocks)))
        ((setter tower-blocks) x (cons y blocks))
      (error <condition>
             (fmt "cannot push block of size ~a on tower ~a" y x)))))

(defgeneric pop (x))

(defmethod pop ((x <tower>))
  (let ((blocks (tower-blocks x)))
    (if blocks
        (progn
          ((setter tower-blocks) x (cdr blocks))
          (car blocks))
      (error <condition>
             (fmt "cannot pop block from empty tower ~a" x)))))

;;;-------------------------------------------------
;;; Move n blocks from tower x1 to tower x2 using x3 as buffer
;;;-------------------------------------------------
(defgeneric move (n x1 x2 x3))

(defmethod move ((n <fpi>) (x1 <tower>) (x2 <tower>) (x3 <tower>))
  (if (= n 1)
      (progn
        (push x2 (pop x1))
        (print x1 nl x2 nl x3 nl nl))
    (progn
      (move (- n 1) x1 x3 x2)
      (move 1 x1 x2 x3)
      (move (- n 1) x3 x2 x1))))

;;;-------------------------------------------------
;;; Initialize and run the 'Towers of Hanoi'
;;;-------------------------------------------------
(defun hanoi ()
  (let ((x1 (make <tower> id: 0))
        (x2 (make <tower> id: 1))
        (x3 (make <tower> id: 2)))
    (build-tower x1 *max-tower-height*)
    (build-tower x2 0)
    (build-tower x3 0)
    (print x1 nl x2 nl x3 nl nl)
    (move *max-tower-height* x1 x2 x3)))

(hanoi)

;;;-------------------------------------------------
)  ;; End of module hanoi
;;;-------------------------------------------------

References

  1. ↑ "Eulisp". https://henry.github.com/EuLisp/Doc/EuLisp-0.991/eulisp.pdf. 
  2. ↑ 2.0 2.1 2.2 "Eulisp". https://github.com/Henry/EuLisp. 
  3. ↑ Kind, Andreas. "Youtoo". England. http://www.cs.bath.ac.uk/~jap/ak1/youtoo/. 

External links



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