lambda-calculus.scm

;; MIT License
;;
;; Copyright (c) 2023 haller33
;;
;; Permission is hereby granted, free of charge, to any person obtaining a copy
;; of this software and associated documentation files (the "Software"), to deal
;; in the Software without restriction, including without limitation the rights
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;; copies of the Software, and to permit persons to whom the Software is
;; furnished to do so, subject to the following conditions:
;;
;; The above copyright notice and this permission notice shall be included in all
;; copies or substantial portions of the Software.
;;
;; THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
;; IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
;; FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
;; AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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;; OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
;; SOFTWARE.

;; this code/core represent the intirety of lambda calculus ...


(load "pmatch.scm")

(define eval-lambda-expr
  (lambda (expr env)
    (pmatch expr
	    [,x (guard (symbol? x))
		      (env x)]
	    [(lambda (,x) ,body)
	     (lambda (arg)
	       (eval-lambda-expr body
                           (lambda(y)
				                     (if (eq? x y)
				                         arg
				                         (env y)))))]
	    [(,rator ,rand)
	     ((eval-lambda-expr rator env)
	      (eval-lambda-expr rand env))])))

;;'((lambda (!)
;;			   (lambda ()
;;				   ((! !))))
;;		   (lambda (!)
;;			   (lambda ()
;;				   ((! !)))))
;;

(define run
  (lambda ()
    (eval-lambda-expr
     '(lambda(x)x)
     (lambda(x)
	     (error 'x "envirompment")))))