# RationalFunctionSign R¶

sign(f, x, a, s) returns the sign of f as x nears a from the left (below) if s is the string "left", or from the right (above) if s is the string "right".
sign(f, x, a) returns the sign of f as x approaches a, from both sides if a is finite.
sign f returns the sign of f if it is constant everywhere.