blob: f15833fa07223986f53883b5abac9b9302aba17f (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
|
#lang eopl
;; <arith-expr> ::== <arith-term> { <add-op> <arith-term> }*
;; <arith-term> ::== <arith-factor> { <mult-op> <arith-factor> }*
;; <arith-factor> ::== <number>
;; <arith-factor> ::== ( <arith-expr> )
;; <add-op> ::== + | -
;; <mult-op> ::== * | /
(define arith-scanner
'(
(add-op (or "+" "-") symbol)
(mult-op (or "*" "/") symbol)
(number (digit (arbno digit)) number)
))
(define arith-grammar
'(
(expression (number) arith-factor)
;(expression (number add-op number) arith-factor)
;(expression (expression add-op expression) arith-factor)
))
(sllgen:make-define-datatypes arith-scanner arith-grammar)
(define list-the-datatypes
(lambda ()
(sllgen:list-define-datatypes arith-scanner arith-grammar)))
(define just-scan
(sllgen:make-string-scanner arith-scanner '()))
(define scan&parse
(sllgen:make-string-parser arith-scanner arith-grammar) )
(define read-eval-print
(sllgen:make-rep-loop "--> " stmt-evaluator
(sllgen:make-stream-parser arith-scanner arith-grammar) ))
|
