guile/step3_env.scm

   1 ;;  Copyright (C) 2015
   2 ;;      "Mu Lei" known as "NalaGinrut" <NalaGinrut@gmail.com>
   3 ;;  This file is free software: you can redistribute it and/or modify
   4 ;;  it under the terms of the GNU General Public License as published by
   5 ;;  the Free Software Foundation, either version 3 of the License, or
   6 ;;  (at your option) any later version.
   7
   8 ;;  This file is distributed in the hope that it will be useful,
   9 ;;  but WITHOUT ANY WARRANTY; without even the implied warranty of
  10 ;;  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  11 ;;  GNU General Public License for more details.
  12
  13 ;;  You should have received a copy of the GNU General Public License
  14 ;;  along with this program.  If not, see <http://www.gnu.org/licenses/>.
  15
  16 (import (readline) (reader) (printer) (ice-9 match) (srfi srfi-43)
  17         (srfi srfi-1) (ice-9 receive) (env))
  18
  19 (define *primitives*
  20   `((+ ,+)
  21     (- ,-)
  22     (* ,*)
  23     (/ ,/)))
  24
  25 (define *toplevel*
  26   (receive (b e) (unzip2 *primitives*)
  27     (make-Env #:binds b #:exprs e)))
  28
  29 (define (READ)
  30   (read_str (_readline "user> ")))
  31
  32 (define (eval_ast ast env)
  33   (define (_eval x) (EVAL x env))
  34   (match ast
  35     ((? symbol? sym) (env-has sym env))
  36     ((? list? lst) (map _eval lst))
  37     ((? vector? vec) (vector-map (lambda (i x) (_eval x)) vec))
  38     ((? hash-table? ht)
  39      (hash-for-each (lambda (k v) (hash-set! ht k (_eval v))) ht)
  40      ht)
  41     (else ast)))
  42
  43 (define (eval_func ast env)
  44   (define expr (eval_ast ast env))
  45   (match expr
  46     (((? procedure? proc) args ...)
  47      (apply proc args))
  48     (else (throw 'mal-error (format #f "'~a' not found" (car expr))))))
  49
  50 (define (EVAL ast env)
  51   (define (->list kvs) ((if (vector? kvs) vector->list identity) kvs))
  52   (define (%unzip2 kvs)
  53     (let lp((next kvs) (k '()) (v '()))
  54       (cond
  55        ;; NOTE: reverse is very important here!
  56        ((null? next) (values (reverse k) (reverse v)))
  57        ((null? (cdr next)) (throw 'mal-error "let*: Invalid binding form" kvs))
  58        (else (lp (cddr next) (cons (car next) k) (cons (cadr next) v))))))
  59   (match ast
  60     ((? (lambda (x) (not (list? x)))) (eval_ast ast env))
  61     (() ast)
  62     (('def! k v) ((env 'set) k (EVAL v env)))
  63     (('let* kvs body)
  64      (let* ((new-env (make-Env #:outer env))
  65             (setter (lambda (k v) ((new-env 'set) k (EVAL v new-env)))))
  66        (receive (keys vals) (%unzip2 (->list kvs))
  67          (for-each setter keys vals))
  68        (EVAL body new-env)))
  69     (else (eval_func ast env))))
  70
  71 (define (PRINT exp)
  72   (and (not (eof-object? exp))
  73        (format #t "~a~%" (pr_str exp #t))))
  74
  75 (define (LOOP continue?)
  76   (and continue? (REPL)))
  77
  78 (define (REPL)
  79   (LOOP
  80    (catch 'mal-error
  81           (lambda () (PRINT (EVAL (READ) *toplevel*)))
  82           (lambda (k . e)
  83             (if (string=? (car e) "blank line")
  84                 (display "")
  85                 (format #t "Error: ~a~%" (car e)))))))
  86
  87 (REPL)