public override Maybe<Result> VisitBasic_expr(QueryParser.Basic_exprContext context)
{
if (context.ADD() != null)
return VisitAdd(context);
if (context.SUB() != null)
return VisitSub(context);
return VisitFact_expr(context.fact_expr());
}
private (Maybe<Result>, Maybe<Result>) VisitTwo(QueryParser.Basic_exprContext context)
{
var left = new BasicExprVisitor(_zmi, _env).Visit(context.basic_expr());
var right = new BasicExprVisitor(_zmi, _env).Visit(context.fact_expr());
return (left, right);
}