Bard College – Computer Science – Design of Programming Languages
This labs gives us practice using lexing and parsing tools to interpret(non-lisp) programs. Specifically, we’ll be processing JavaScript Object Notation(JSON). From Eloquent JavaScript,“JSON is widely used as a data storage and communication format on the Web, even in languages other than JavaScript.” Fun data sets represented in JSON can be found in Darius Kazemi’s corpora project.
Warm Up: Infix Expressions
Use sllgen and define-datatype to parse infix expressions(from Exercise B.1).
Warm Up: Infix Expressions
#lang racket(require eopl)
(define the-lexical-spec '((whitespace (whitespace) skip) (mul-op ("*") symbol) (add-op ("+") symbol) (number (digit (arbno digit)) number)))
(define the-grammar '((a-expr ;:== (a-term (arbno add-op a-term)) binop) (a-term ;:== (a-factor (arbno mul-op a-factor)) binop) (a-factor ;:== (number) number) (a-factor ;:== ("(" a-expr ")") factor)))
(define-datatype infix infix? (binop (left infix?) (operators (list-of symbol?)) (right (list-of infix?))) (factor (value infix?)) (number (value integer?)))
(define just-scan (sllgen:make-string-scanner the-lexical-spec the-grammar))
(define scan&parse (sllgen:make-string-parser the-lexical-spec the-grammar))
(display (just-scan "2 + 3 * 4"))(newline)(display (scan&parse "2 + 3 * 4"))(newline)