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module lang::flybytes::demo::pico::Syntax

rascal-0.42.0
org.rascalmpl.flybytes-0.2.11

Usage​

import lang::flybytes::demo::pico::Syntax;

Dependencies​

import ParseTree;

syntax Program​

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

syntax Declarations​

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

syntax IdType​

syntax IdType = idtype: Id id ":" Type t;

syntax Statement​

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

syntax Type​

syntax Type 
  = natural:"natural" 
  | string :"string" 
  | nil    :"nil-type"
  ;

syntax Expression​

syntax Expression 
  = id: Id name
  | strcon: String string
  | natcon: Natural natcon
  | bracket "(" Expression e ")"
  > left concat: Expression lhs "||" Expression rhs
  > left ( add: Expression lhs "+" Expression rhs
         | min: Expression lhs "-" Expression rhs
         )
  ;

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 
   = [\ \t\n\r]
   | @category="Comment" "%" ![%]+ "%"
   | @category="Comment" "%%" ![\n]* $
   ;

function program​

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

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