Talk:Period of a function

Minimal period

The article states "If a real-valued function $f$ of a real argument is periodic on $X$ (and is not identically equal to a constant), then it has a least period $T_0>0$". And yet the Dirichlet function $D(x)$, presented two sentences earlier, has no such minimum period. Presumably some extra condition is missing? Richard Pinch (talk) 23:06, 20 October 2017 (CEST)

How ridiculous: a statement follows its counterexample... Well, the Russian version contains the adjective "continuous" (but "periodic" is missing there). I'll add "continuos" here. Boris Tsirelson (talk) 09:28, 21 October 2017 (CEST)