How can I eliminate left recursion in the following grammar?

Question

Here's a grammar that should describe the language of enclosed braces with commas as separators:

L ::= {L} | L,L | 

A few examples of lines that I would expect the grammar to accept and reject:

Accept:

 {,{,,{,}},,{,}} {{{{}}}} {,{}} 

Reject

 {}{} {,{}{}} {{},{} 

Answer 1

Manually done:

L :: = { L } | { L } , | , L | & Epsilon;

Or instead of just using wings, we could use a more systematic approach and apply the algorithm from Wikipedia to remove the immediate left recursion :

L :: = { L } L ₁ | L <sub> 1sub>
L ₁ :: =? | , LL ₁

Answer 2

First of all, this grammar will not take your first example, since it requires the commas to be after the closing bracket and before the open curly bracket. I would suggest rewriting it as

 L::= {L} | ,L 

This will not save you from left recursion, but at least will match your acceptable answers.