This data structure is called the zipper, and the neat thing is that you can generalize this to more complicated types like trees: https://www.st.cs.uni-saarlan

This data structure is called the zipper, and the neat thing is that you can generalize this to more complicated types like trees: https://www.st.cs.uni-saarland.de/edu/seminare/2005/advanced-fp/docs/huet-zipper.pdf https://www.st.cs.uni-saarland.de/edu/seminare/2005/advanced...