Definition:Antiperiodic Function/Antiperiod

Definition
Let $f: X \to X$ be an anti-periodic function, where $X$ is either $\R$ or $\C$.

The anti-period of $f$ is the smallest value $\cmod L \in \R_{\ne 0}$ such that:
 * $\forall x \in X: - \map f x = \map f {x + L}$

where $\cmod L$ is the modulus of $L$.