On Scottish Book problem 157. (English) Zbl 1384.26021

Summary: This paper descibes our hunt for the solver of Problem 157 in the Scottish Book, a problem originally posed by A. J. (Gus) Ward in 1937. We first make the observation that a theorem of Richard O’Malley from 1975 yields an immediate positive solution. A further look at O’Malley’s references revealed a 1970 paper by Donald Ornstein that we now believe contains the first solution of SB 157. We isolate the common elements in the machinery used by both Ornstein and O’Malley and discuss several consequences. We also examine an example function given by Ornstein. There are some difficulties with this function but we provide a fix, and show moreover that functions of that kind are typical in the sense of the Baire category theorem.


26A24 Differentiation (real functions of one variable): general theory, generalized derivatives, mean value theorems
26A48 Monotonic functions, generalizations
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