EuLisp

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EuLisp
EuLispLogo.png
Paradigmmulti-paradigm: functional, procedural, meta, object-oriented
FamilyLisp
First appeared1990; 28 years ago (1990)
Preview release
0.991[1] / 2010; 8 years ago (2010)
Typing disciplinestrong, 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[edit]

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) was available in 1990.

Distinguishing features[edit]

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[edit]

Implementations[edit]

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 EuSchemeEuScheme 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[edit]

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[edit]

  1. ^ "Eulisp" (PDF). GitHub.
  2. ^ a b c "Eulisp". GitHub.
  3. ^ Kind, Andreas. "Youtoo". School of Mathematical Sciences. University of Bath. England. Retrieved 2018-10-28.

External links[edit]