How to parse expression with parenthesis?

I would like to parse an expression with parenthesis in python using textx.

For example the following DSL :

CREATE boby = sacha - ( boby & tralaa) ; 

CREATE boby = sacha & boby - ( david & lucas )

This is the grammar I tried:

Model:
    'CREATE' name=Identifier '=' exp=SetExpr
;

JoinOperator: /-/&/;

SetExpr:SetParExpr | SetBaseExpr 
;

SetBaseExpr:
    first=ID op=JoinOperator second=ID
;

SetParExpr:
    '(' SetExpr ')'

I guess I should have a list somewhere to fill with expression. Do you have any suggestion ?

I've changed your examples just slightly: I added a semicolon to end and I put another pair of parentheses in your second example. I inferred these changes based on what you provided in your grammar. Here's the examples:

CREATE boby = sacha - ( boby & tralaa);

CREATE boby = sacha & (boby - ( david & lucas ));

To parse examples like these your grammar needs to be changed to:

1. Take in multiple Models (I created a Script rule that takes semi colon separated models)
2. Allow the second property of the SetBaseExpr rule to be an ID or a SetParExpr.
3. Change Identifier to ID in the model rule (I assume this is what you meant).

I made these changes and ended up with the following grammar that parses the examples I gave:

Script:
    models+=Model[';'] ';'
;

Model:
    'CREATE' name=ID '=' exp=SetExpr
;

JoinOperator: '-' | '&';

SetExpr:
    SetParExpr | SetBaseExpr
;

SetBaseExpr:
    first=ID op=JoinOperator (second=ID | second=SetParExpr)
;

SetParExpr:
    '(' SetExpr ')'
;

I hope that answers your question or gives you a hint as to handle parenthetical expressions.