Infinite chess is any variation of the game of chess played on an unbounded chessboard. Variations of chess played on an unbounded board are called infinite chess. This inequality may be used to obtain exponential inequalities for unbounded variables. Exponential search extends binary search to unbounded lists. These concepts are undefined for empty or unbounded intervals. A bounded input that produces an unbounded output is sgn(sinc("t")). See also Extensions of symmetric operators and unbounded operator. It has been shown that any inflationary theory with an unbounded potential is eternal. A class is stationary if it has a nonempty intersection with every closed unbounded class. Dijkstra argued that it was impossible to implement unbounded nondeterminism. A linear program can also be unbounded or infeasible. Any Liouville number must have unbounded partial quotients in its continued fraction expansion. The definition of normal operators naturally generalizes to some class of unbounded operators. The notion of spectrum extends to unbounded operators. A LP can also be unbounded or infeasible.