Here's an Irony Grammar [1] that can parse the proposed problem if the missing "a point halfway between" is added. And a screenshot of the Grammar Explorer [2]

Here's an Irony Grammar [1] that can parse the proposed problem if the missing "a point halfway between" is added. And a screenshot of the Grammar Explorer [2] for the lazy ones. It was fun to write :). [1] https://gist.github.com/guillaume86/6423775 https://gist.github.com/guillaume86/6423775 [2] https://dl.dropboxusercontent.com/u/177896/SolLewitt.PNG https://dl.dropboxusercontent.com/u/177896/SolLewitt.PNG