grammar EasyCalc;

program : declar$*$ stmt$*\text{'}$$$$\text{'}$;

declar : type$=(\text{'}$bool$\text{'}|$ 'int' $|$ 'real'$)$ ID $\text{'}$;$\text{'}$;

stmt : ID $\text{'}$:$=\text{'}$ expr $\text{'}$;$\text{'}$ # AssignStmt

$|$ 'read' ID $\text{'}$;$\text{'}$ # ReadStmt

$|$ 'write' expr $\text{'}$;$\text{'}$ # WriteStmt

;

expr : LIT # LitExpr

$|$ ID # IdExpr

$|\text{'}(\text{'}$ expr $\text{'})\text{'}$ # ParenExpr

$|$ op$=(\text{'}$to$\_$int'$|\text{'}$to$\_$real'$)\text{'}(\text{'}$ expr $\text{'})\text{'}$ # ToExpr

$|$ expr op$=(\text{'}*\text{'}|\text{'}/\text{'})$ expr # MulDivExpr

$|$ expr op$=(\text{'}+\text{'}|\text{'}-\text{'})$ expr # AddSubExpr

$|$ expr op expr # LessGrtrExpr

$|$ expr op$=\text{'}==\text{'}$ expr # EqualExpr

$|$ expr op$=$'and' expr # AndExpr

$|$ expr op$=\text{'}$or$\text{'}$ expr # OrExpr

$|\text{'}$if$\text{'}$ expr 'then' expr 'else' expr # IfExpr

;

DSTOP : $\text{'}$$$$\text{'}$;

SSTOP : $\text{'}$;$\text{'}$;

BOOL : 'bool';

INT : 'int';

REAL : 'real';

ASSIGN : $\text{'}$:$=\text{'}$;

READ : 'read';

WRITE : 'write';

LPAREN : $\text{'}(\text{'}$;

RRAPEN : $\text{'})\text{'}$;

TINT : $\text{'}$to$\_$int';

TREAL : $\text{'}$to$\_$real';

MUL : $\text{'}*\text{'}$;

DIV : $\text{'}/\text{'}$;

ADD : $\text{'}+\text{'}$;

SUB : $\text{'}-\text{'}$;

LESS : $\text{'}<mi\; id="EditorElement\_867474">\text{'}</mi>$;

GRTR : $\text{'}>\text{'}$;

EQUAL : $\text{'}==\text{'}$;

AND : 'and';

OR : $\text{'}$or$\text{'}$;

IF : $\text{'}$if$\text{'}$;

THEN : 'then';

ELSE : 'else';

LIT : $[0-9]+|([0-9]*(\text{'}.\text{'}[0-9]|[0-9]\text{'}.\text{'})[0-9]*)|$ 'true' $|\text{'}$false$\text{'}$;

ID : $[$a$-$zA$-$Z$][$a$-$zA$-$Z$0-9\_]*$;

WS : $[\backslash$t$\backslash$r

$]+->$ skip;

$//====================$

$//====================$

$//====================$

package easycalc;

import java.util.$*$;

import org.antlr.v$4.$runtime.$*$;

import org.antlr.v$4.$runtime.tree.$*$;

import easycalc.grammar.$*$;

public class PrettyPrinterApp $\{$

public static void main$($String$[]$ args$)\{$

$//====================$

$//$ Read in multiple lines of input

$//====================$

StringBuilder sb $=$ new StringBuilder$()$;

Scanner scan $=$ new Scanner$($System$.$in$)$;

String nextLine $=$ scan.nextLine$()$;

while $(!$nextLine.contains$("$$$$"))\{$

sb$.$append$($nextLine$)$;

scan $=$ new Scanner$($System$.$in$)$;

nextLine $=$ scan.nextLine$()$;

$\}$

scan.close$()$;

sb$.$append$($nextLine$)$;

String str $=$ sb$.$toString$()$;

$//====================$

$//$ Create the parse tree from the input stream

$//====================$

CharStream input $=$ CharStreams.fromString$($str$)$;

EasyCalcLexer lexer $=$ new EasyCalcLexer$($input$)$;

CommonTokenStream tokens $=$ new CommonTokenStream$($lexer$)$;

EasyCalcParser parser $=$ new EasyCalcParser$($tokens$)$;

ParseTree tree $=$ parser.program$()$; $//$ begin parsing at program rule

$//==================$

$//$ Walk the tree with the pretty$-$print listener

$//===================$

ParseTreeWalker walker $=$ new ParseTreeWalker$()$; $//$ create standard walker

PrettyPrinterListener printer $=$ new PrettyPrinterListener$()$;

walker.walk$($printer$,$ tree$)$; $//$ initiate walk of tree with listener

System.out.println$($printer$.$getProgramString$())$; $//$ pretty print program

$\}$

$//===============$

$//===============$

$//===============$

package easycalc;

$//$import easycalc.grammar.EasyCalcBaseListener;

import easycalc.grammar.$*$;

import java.util.Scanner;

public class PrettyPrinterListener extends EasyCalcBaseListener $\{$

$//===================$

$//$ Read in Multiple lines of input

$//====================$

private final StringBuilder sb $=$ new StringBuilder$()$;

public String getProgramString$()\{$

return sb$.$toString$()$;

$\}$

public void exitDeclar$($EasyCalcParser$.$DeclarContext ctx$)\{$

sb$.$append$($ctx$.$type.getText$()).$append$("").$append$($ctx$.$ID$().$getText$()).$append$("$;

$")$;

$\}$

$\}$