[antlr-interest] Re: Semantic predicates that aren't & hoisting

[John D. Mitchell]

>>>>> "David" == David Jung <jungdl at ornl.gov> writes:
[...]

Ugh.  Well, if you want me to fix your wacky grammar/language, I'll have to
start charging you my consulting rate.


Here's a relatively proper language that deals with statements and
expressions with the nesting that you seem to want.

Here's a sample input: {if (a() < 0) then {b; c(); {;} dd();} e; f();} g();

Note very clearly that the blocks do NOT require a semi-colon where as a
bare expression (when used as a statement) does.


<<<<< ExprList.g <<<<<

/*
 * Lex and parse a silly little language showing how to do nesting in a list.
 */

header
{
import java.io.* ;
import antlr.* ;
}

class ExprListParser extends Parser;

options
{
k = 2;
buildAST = false;
}

{
}


program : statementList EOF ;

statementList : ( statement )* ;

statement
        : SEMI
        | block
        | expression SEMI
        | "if" LPAREN expression RPAREN "then" statement
          ( options { warnWhenFollowAmbig = false; } : "else" statement )?
        ;

block : LCURLY statementList RCURLY ;

expression : equalityExpr ;

equalityExpr : relationalExpr ( ( EQUAL | NOT_EQUAL ) relationalExpr )* ;

relationalExpr : postfixExpr ( ( LT | LTE | GT | GTE ) postfixExpr )* ;

postfixExpr : primaryExpr ( postfixSuffix )? ;

primaryExpr
        : ID
        | intConst
        ;

postfixSuffix : ( functionCall )+ ;

functionCall : LPAREN RPAREN ;

protected
intConst : IntLiteral ;



{
import java.io.* ;
import antlr.* ;
}


class ExprListLexer extends Lexer;

options
{
k = 3;
testLiterals = false;
}

{
}

protected
Vocabulary : '\3'..'\377' ;

SEMI : ';' ;

LCURLY : '{' ;
RCURLY : '}' ;
LPAREN : '(' ;
RPAREN : ')' ;

EQUAL       : "==" ;
NOT_EQUAL   : "!=" ;
LTE         : "<=" ;
LT          : "<" ;
GTE         : ">=" ;
GT          : ">" ;

Whitespace
        : ( ( '\003'..'\010'
            | '\t'
            | '\013'
            | '\f'
            | '\016'..'\037'
            | '\177'..'\377'
            | ' ' )
          | "\r\n"        { newline(); }
          | ( '\n' | '\r' )     { newline(); }
          )                     { _ttype = Token.SKIP;  }
        ;

protected
Digit : '0'..'9' ;

IntLiteral : ( Digit )+ ;

ID
options { testLiterals = true; }
        : ( 'a'..'z' | 'A'..'Z' | '_' )
          ( 'a'..'z' | 'A'..'Z' | '_' | '0'..'9' )*
        ;

>>>>> >>>>>


<<<<< ExprListTest.java <<<<<
/*
 * This example shows how to do a nested list inside an expression.
 */

import java.io.* ;

import antlr.* ;

public class ExprListTest
    {
    public static void main (String[] args)
	{
	if (0 >= args.length)
	    {
	    spewLine ("Usage: java ExprListTest file+");
	    }

	for (int argNum = 0; argNum < args.length; argNum++)
	    {
	    try
		{
		DataInputStream input = null;

		String progName = args[argNum];

		if ("--".equals (progName))
		    {
		    input = new DataInputStream (System.in);
		    }
		else
		    {
		    input = new DataInputStream
			( new FileInputStream (progName) );
		    }

		ExprListLexer lexer = new ExprListLexer (input);

		ExprListParser parser = new ExprListParser (lexer);
		
		try
		    {
		    parser.program();
		    }
		catch (TokenStreamException ex)
		    {
		    spewLine ("Unable to read data from '" + progName + "'!",
			      ex);
		    }
		catch (RecognitionException ex)
		    {
		    spewLine ("Unable to parse data from '" + progName + "'!",
			      ex);
		    }
		}
	    catch (Exception ex)
		{
		spewLine ("Unknown exception:", ex);
		}
	    }
	}

    private static void spewLine (String s, Exception ex)
	{
	System.err.println (s);
	ex.printStackTrace();
	System.exit (1);
	}
    
    private static void spewLine (String s)
	{
	System.err.println (s);
	System.exit (1);
	}
    
    }

>>>>> >>>>>

Take care,
	John