Transform grammar to avoid common prefixes

Question

I have this grammar with common prefixes (<id>) and I want to transform it to avoid them.

void Components() : {}
{
    (Read() | Write())* (<id>Assignment())* <id>Declaration() (Read() | Write() | <id>(Assignment() | Declaration()))*
}

The problem is (<id>Assignment())* <id>Declaration(). The grammar can have 0 or more Assignments/Read/Write statments but at least 1 Declaration and then any statment/declaration in any order.

Answer 1

Refactoring this is easy, but I probably wouldn't do it. I'd probably look ahead a little further. Here are two solutions

---

Factor out the <id>

void Components() : {}
{
    (Read() | Write())*
    <id>
    (Assignment() <id>)*
    Declaration()
    ( Read()
    | Write()
    | <id> (Assignment() | Declaration())
    )*
}

---

Use longer lookahead

void Components() : {}
{
    (Read() | Write())*
    (LOOKAHEAD( 2 ) <id> Assignment())*
    <id> Declaration()
    ( Read()
    | Write()
    | LOOKAHEAD( 2 ) <id> Assignment()
    | <id> Declaration())
    )*
}