Foundations of Software - LAMP - EPFL

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A JSON parser package examples.parsing // import the standard parser class import scala.util.parsing.combinator.syntactical.StandardTokenParsers object JSON extends StandardTokenParsers { // fix some delimiter symbols ... lexical.delimiters += (”{”, ”}”, ”[”, ”]”, ”:”) // ... and some reserved words lexical.reserved += (”null”, ”true”, ”false”) // here are the four productions making up the JSON grammar def obj : Parser[Any] = ”{” ˜ repsep(member, ”,”) ˜ ”}” def arr : Parser[Any] = ”[” ˜ repsep(value, ”,”) ˜ ”]” def member : Parser[Any] = stringLit ˜ ”:” ˜ value def value : Parser[Any] = stringLit | numericLit | obj | arr | ”null” | ”true” | ”false” 46
Testing the JSON Parser Add a method main that can be used to test the parser. def main(args : Array[String]) { val tokens = new lexical.Scanner(args(0)) println(args(0)) println(phrase(value)(tokens)) } Here are two test runs: >java examples.parsing.JSON ”{ ”x”: true, ”y”: [1, 2, 3] }” { x : true, y : [1, 2, 3] } [1.26] parsed : (({ ˜ List(((x ˜ :) ˜ true), ((y ˜ :) ˜ (([ ˜ List(1, 2, 3)) ˜ ])))) ˜ }) 47
Page 1 and 2: Foundations of Software Martin Oder
Page 3 and 4: What is “software foundations”?
Page 5 and 6: What you can expect to get out of t
Page 7 and 8: What this course is not � An intr
Page 9 and 10: Overview This course will concentra
Page 11 and 12: Organization of the Course 11
Page 13 and 14: Information Textbook: Types and Pro
Page 15 and 16: Homework and Projects You will be a
Page 17 and 18: Learning Scala If you don’t know
Page 19 and 20: Collaboration � Collaboration on
Page 21 and 22: Part I Modelling programming langua
Page 23 and 24: Approaches to Parsing There are two
Page 25 and 26: Embedded Domain Specific Languages
Page 27 and 28: � Option [...] is now expressed b
Page 29 and 30: The Basic Idea For each language (i
Page 31 and 32: In each case, chars represents the
Page 33 and 34: Object-Oriented Parser Combinators
Page 35 and 36: Specific Single-Token Parsers � T
Page 37 and 38: The Sequence Combinator � The seq
Page 39 and 40: The Alternative Combinator � The
Page 41 and 42: Result Conversion The parser P ˆˆ
Page 43 and 44: The Interleaved Repetition Combinat
Page 45: An Example: JSON JSON, or JavaScrip
Page 49 and 50: Getting Better Output � The resul
Page 51 and 52: Table of Parser Combinators ident i
Page 53 and 54: A Problem with Top-Down Parsing As
Page 55 and 56: ... and reduce is defined as follow

Foundations of Software - LAMP - EPFL

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