popl.g4

// Python Parser Project
// By Dhruv Agarwal, Andrew Chang, Ryan Huynh, Adi Pillai, and Ashwin Prayaga

grammar popl;

tokens { INDENT, DEDENT }

// Lexer code for antlr-denter
@lexer::header {
  import com.yuvalshavit.antlr4.DenterHelper;
}

@lexer::members {
  private final DenterHelper denter = DenterHelper.builder()
    .nl(NL)
    .indent(poplParser.INDENT)
    .dedent(poplParser.DEDENT)
    .pullToken(poplLexer.super::nextToken);

  @Override
  public Token nextToken() {
    return denter.nextToken();
  }
}

NL: ((' ' | '\t')* '\r'? '\n' '\t'*);
NOT: 'not';
BOOLCOMP: 'and' | 'or' | 'in';
MATHCOMP: '==' | '>=' | '<=' | '>' | '<' | '!=';
INT: [0-9]+;
STRING: ('"' .*? '"' ) | ('\'' .*? '\'') | ('"""' .*? '"""');
VAR: [a-zA-Z_][a-zA-Z0-9_]*;
SPACE: ' ' | '\t';
COMMENT:  '#' (~'\n')*;
MULTILINECOMMENT: ('"""' .*? '"""')+ | ('\'\'\'' .*? '\'\'\'')+ ;

start: statement* EOF;

basestatement: assign NL
    | expr NL
    | MULTILINECOMMENT NL
    | funcblock
    | funccall;

statement: basestatement
    | COMMENT NL
    | ifblock elifblock* elseblock?
    | whileblock elseblock?
    | forblock elseblock?;

funcstatement: basestatement
    | funcifblock funcelifblock* funcelseblock?
    | funcwhileblock funcelseblock?
    | funcforblock funcelseblock?
    | funcreturn;

// Arithmetic operators
expr: expr SPACE* ('*' | '/' | '+' | '-' | '%') SPACE* expr SPACE* COMMENT?
    | INT
    | VAR
    | STRING
    | funccall
    | '(' expr ')';

// Assignment operators
assign: VAR SPACE* ('=' | '+=' | '-=' | '*=' | '/=') SPACE* expr SPACE* COMMENT?;

// Conditional statements
conditional: (SPACE* MATHCOMP SPACE* | SPACE+ BOOLCOMP (SPACE+ | SPACE+ NOT SPACE+)) expr conditional
    | /* epsilon */;
forconditional: VAR SPACE* 'in' SPACE* VAR;

body: (statement | NL | COMMENT NL)* statement (statement | NL | COMMENT NL)* ;
funcbody: (funcstatement | NL | COMMENT NL)* funcstatement (funcstatement | NL | COMMENT NL)* ;

// if, elif, else, while, and for
ifstatement: 'if' SPACE+ (NOT SPACE+)? expr conditional SPACE* ':' SPACE* COMMENT?;
ifblock: ifstatement INDENT body DEDENT;
funcifblock: ifstatement INDENT funcbody DEDENT;

elifstatement: 'elif' SPACE+ (NOT SPACE+)? expr conditional SPACE* ':' SPACE* COMMENT?;
elifblock: elifstatement INDENT body DEDENT;
funcelifblock: elifstatement INDENT funcbody DEDENT;

elsestatement: 'else' SPACE* ':' SPACE* COMMENT*;
elseblock: elsestatement INDENT body DEDENT;
funcelseblock: elsestatement INDENT funcbody DEDENT;

whilestatement: 'while' SPACE+ (NOT SPACE+)? expr conditional SPACE* ':' SPACE* COMMENT?;
whileblock: whilestatement INDENT body DEDENT;
funcwhileblock: whilestatement INDENT funcbody DEDENT;

forstatement: 'for' SPACE+ forconditional SPACE* ':' SPACE* COMMENT?;
forblock: forstatement INDENT body DEDENT;
funcforblock: forstatement INDENT funcbody DEDENT;


// Function implementations
args: (SPACE* VAR SPACE* (',' SPACE* VAR SPACE*)*)*;
funcdefinition: 'def' SPACE+ VAR SPACE* '(' args ')' SPACE* ':' SPACE* COMMENT?;
funcreturn: 'return' SPACE* expr? SPACE* COMMENT?;
funcblock: funcdefinition INDENT funcbody DEDENT;


// Function calls
callargs: (SPACE* expr SPACE* (',' SPACE* expr SPACE*)*)*;
funccall: VAR SPACE* '(' callargs ')' SPACE* COMMENT?;

// Function returns for loops and conditionals

reserved:
     'False' | 'def' | 'if' | 'raise'
    | 'None' | 'del' | 'import' | 'return' | 'True'
    | 'elif' | 'in' | 'try' | 'and' | 'else'
    | 'is'| 'while' | 'as'
    | 'except' | 'lambda' | 'with' | 'assert' 
    | 'finally' | 'nonlocal' | 'yield' | 'break'
    | 'for' | 'not'| 'class' | 'from' | 'or'
    | 'continue' | 'global' | 'pass';