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module demo::lang::Pico::Syntax

rascal-0.34.0

Usage​

import demo::lang::Pico::Syntax;

Dependencies​

import ParseTree;

syntax Id​

lexical Id = [a-z][a-z0-9]* !>> [a-z0-9];

syntax Natural​

lexical Natural = [0-9]+ ;

syntax String​

lexical String = "\"" ![\"]*  "\"";

syntax Layout​

layout Layout = WhitespaceAndComment* !>> [\ \t\n\r%];

syntax WhitespaceAndComment​

lexical WhitespaceAndComment      ❷  
   = [\ \t\n\r]
   | @category="Comment" ws2: "%" ![%]+ "%"      ❸  
   | @category="Comment" ws3: "%%" ![\n]* $      ❸  
   ;

syntax Program​

start syntax Program      ❹  
   = program: "begin" Declarations decls {Statement  ";"}* body "end" ;

syntax Declarations​

syntax Declarations 
   = "declare" {Declaration ","}* decls ";" ;

syntax Declaration​

syntax Declaration = decl: Id id ":" Type tp;

syntax Type​

syntax Type 
   = natural:"natural" 
   | string :"string" 
   ;

syntax Statement​

syntax Statement 
   = asgStat: Id var ":="  Expression val 
   | ifElseStat: "if" Expression cond "then" {Statement ";"}*  thenPart "else" {Statement ";"}* elsePart "fi"
   | whileStat: "while" Expression cond "do" {Statement ";"}* body "od"
  ;

syntax Expression​

syntax Expression      ❺  
   = id: Id name
   | strCon: String string
   | natCon: Natural natcon
   | bracket "(" Expression e ")"
   > left conc: Expression lhs "||" Expression rhs
   > left ( add: Expression lhs "+" Expression rhs
          | sub: Expression lhs "-" Expression rhs
          )
  ;

function program​

start[Program] program(str s) {
  return parse(#start[Program], s);
}

start[Program] program(str s, loc l) {
  return parse(#start[Program], s, l);
}