Integer programming easily encloses horse

- The "horse" in the title is a reference to a famous 2003 paper ("A horse is a horse, of course, of course") that used integer programming—a method for solving optimization problems with yes/no decisions—to prove that a particular protein fold can't exist in nature. The paper became a cult classic in computational biology. - Integer programming (IP) is a branch of math/computer science for solving problems where variables must be whole numbers (e.g., 0 or 1). It's used to find optimal solutions given constraints, like scheduling or logistics. - This article explores how IP can formally rule out hypothetical biological structures (like the "horse" fold) by proving they violate physical or geometric constraints. The title's playful phrasing ("encloses") points to the idea of logically fencing in a possibility space. - The broader significance: IP methods are increasingly used in bioinformatics, materials science, and engineering to test whether a proposed structure is physically possible before building or simulating it.