//
// WRITE A CORRECT GRAMMAR FOR THE TINY LANGUAGE IN THIS FILE.
//
// The grammar is described in data/tinyGrammar.pdf. Do not use dashes
// in your non-terminal names. I recommend you use mixed case naming for your
// non-terminals instead (e.g. stmtSeq).
//
// Do not put any string literals in this grammar (e.g. "="). Use only token
// names given in TinyLexer.tokens.
//
// This file contains an expression grammar that uses tokens described in
// TinyLexer.tokens.
//
// NOTE ONE ERROR in the pdf: the second production rule should read:
//    stmt-seq -> stmt-seq stmt | stmt

grammar Tiny;

goal: program;

program: stmtseq;

stmtseq: stmtseq stmt
        | stmt;

stmt: ifstmt
     | repeatstmt
     | assignstmt
     | readstmt
     | writestmt
     ;

ifstmt: IF exp THEN stmtseq END
       | IF exp THEN stmtseq ELSE stmtseq END
       ;

repeatstmt: REPEAT stmtseq UNTIL exp;

assignstmt: ID EQUAL exp;

readstmt: READ ID;

writestmt: WRITE exp;

exp: simpleexp LT simpleexp
    | simpleexp EQUAL simpleexp
    | simpleexp
    ;

simpleexp: simpleexp PLUS term
          | simpleexp MINUS term
          | term
          ;

term: term MULTIPLY factor
     | term DIVIDE factor
     | factor
     ;

factor: OPAREN exp CPAREN
       | NUM
       | ID
       ;