anchor.diff:  // 'input' | 'print' |  // <- para el ejemplo del blog
   'if'| 'then'| 'else'| 'unless'| 'while'| 'loop'| 'for'| 'foreach'| 'each'| 'do'| 'in'| 'between'
   | 'when'| 'case'| 'switch'| 'repeat'| 'until'| 'try'| 'catch'| 'except'| 'on'| 'select'| 'from'| 'where'| 'class'| 'struct'| 'begin'| 'end'| 'program'| 'interface'| 'implementation'| 'uses'| 'import'| 'package'| 'module'| 'super'| 'this'| 'me'| 'self'| 'break'| 'go'| 'to'| 'goto'| 'downto'| 'default'| 'ensure'| 'rescue'| 'require'
  -| '<'| '>'| '<>'| '<='| '>='| '<=>'| '='| '=='| '=/='| '/'| '/='| '*'| '*=' | '+'| '+='| '-'| '-='| '~'| '~='| '^'| '^='| '&'| '&='| '&&'| '|'| '||'| '|='| 'and'| 'or'| 'not'| '!'| '!='| '!!'| '@'| '#'| '$'| '%'| 'mod'| 'div' ;
  +| '<'| '>'| '<>'| '<='| '>='| '<=>'| '='| '=='| '=/='| '=~' | '/'| '/='| '*'| '*=' | '+'| '+='| '-'| '-='| '~'| '~='| '^'| '^='| '&'| '&='| '&&'| '|' | '||'| '|='| 'and'| 'or'| 'not'| '!'| '!='| '!!'| '@'| '#'| '$'| '%'| '?' | 'mod'| 'div' ;
   
  -operand : STRING | TOKEN ;
  +operand
  +	: TOK
  +	| STRING
  +	;
   
  -STRING : '"' .*? '"' | '\'' .*? '\'' ;
   
  -TOKEN : [_a-zA-Z0-9]+;
  +TOK : [_a-zA-Z0-9]+ 
  +	  | ESC_SEQ
  +	  ;
   
  -WS : [ \t\r\n\(\)\[\]\{\}\.\,\:\;]+ -> skip;
  +
  +STRING
  +    :  '"' ( ESC_SEQ |  ~('\\'|'"') )* '"'
  +    |  '\'' ( ESC_SEQ | ~('\\'|'\'') )* '\''
  +    ;
  +
  +fragment
  +ESC_SEQ
  +    :   '\\' ( '\"'  | '\''  | '\\' | '|' | [a-zA-Z0-9]+ | '(' | ')' | '{' | '}' | '[' | ']' 
  +    | '+' | '*' | '-' | '/' | '^' | '%' | '$' | '&' | '<' | '>' | '=' | '~' | '!'
  +    | '@' | '#' | '.' | ',' | ';' | ':' | '?' | '\n' | '\r') ;
  +
  +
  +WS : ([ \r\n\t] | '(' | ')' | '[' | ']' | '{' | '}' | '.' | ';' | ':' | ',')+ -> skip;
  
positive.code: grammar Halstead;
  
  @header {
  	import java.util.*;
  
negative.code: 
  	  };
  
  e : token* {
  			int n1 = operators.keySet().size();
  
  			int N1 = operatorsList.size();
  
  			int n2 = operands.keySet().size();
  
  			int N2 = operandsList.size();
  
  			int N = N1 + N2;
  			int n = n1 + n2;
  
  			double V = N*log2(n);
  			double D = (n1/2.0)*(N2/(double)n2);
  			double L = 1.0/D;
  			double E = V*D;
  
  			println("E = "+E);
  			println("T = "+(E/18.0));
  
  
  
  	  };
  
  token 
  	: operator { 
  		String op = $operator.text;
  