There Is No Word A Poem by Tony Hoagland www.poetryfoundation.org what I already am thinking about is my gratitude for language— how it will stretch just so much and no farther; how there are some holes it will not cover up; how it will move, if not inside, then around the circumference of almost anything— how, over the years, it has given me back all the hours and days, all the plodding love and faith, all the misunderstandings and secrets I have willingly poured into it. languagewords
Wang tiles Wang tiles (Hao Wang, 1961) are a class of formal systems. They are modelled visually by square tiles with a color on each side. A set of such tiles is selected, and copies of the tiles are arranged side by side with matching colors, without rotating or reflecting them. The basic question about a set of Wang tiles is whether it can tile the plane or not, i.e., whether an entire infinite plane can be filled this way. The next question is whether this can be done in a periodic pattern. In 1966, Wang's student Robert Berger solved the problem in the negative. He proved that no algorithm for the problem can exist, by showing how to translate any Turing machine into a set of Wang tiles that tiles the plane if and only if the Turing machine does not halt. The undecidability of the halting problem then implies the undecidability of Wang's tiling problem. Wikipedia en.wikipedia.org Truchet TilesThe Tiling Patterns of Sebastien Truchet and the Topology of Structural Hierarchy mathalgorithms