Comment by dalke

I can't figure out the grammar. I wanted to do the Hilbert curve at https://en.wikipedia.org/wiki/Hilbert_curve:

    Alphabet : A, B
    Constants : F + −
    Axiom : A
    Production rules:
        A → +BF−AFA−FB+
        B → −AF+BFB+FA−

I thought it might be:

  A=|+[B]|−[A]|[A]-|[B]+
  B=|−[A]|+[B]|[B]+|[A]−

but that doesn't work, and I don't know what's wrong.