Question

I need “{” will be single on a line. Therefore I have to use a token that recognize it. This are right examples:

program
{

or

program



{

And this are incorrect examples:

program { 

or

program 
{ sentence;

Then I have a token like this:

TOKEN: { < openKey: "{" >   {System.out.print(image +"\n");}}
SKIP: { < ( " " | "\r" | "\t" | "\n" )+ > }

But I can not think how to make the symbol “{” is exactly between one or more “\n”. And after recognized it I have to write exactly:

program
{

If I try:

TOKEN: { < openKey: ( " " | "\r" | "\t" | "\n" )+ "{" ( " " | "\r" | "\t" | "\n" )+ >   {System.out.print(image +"\n");}}

This runs but it writes so many “\n” like there was in the input.

Answer 1

I did it differently:

TOKEN: { < openKey: "\n" (" " | "\t")* "{" (" " | "\t")* ("\r" | "\n") >{System.out.print("{\r\n");}}   
SKIP: { " " | "\r" | "\t" | "\n" }

There were some problems with the carriage return, but this way works well.