What does this dollar sign over arrow in function mapping mean? In a certain function mapping like this, $x \xleftarrow{\$} \\{0,1\\}^k$ (Lecture Notes on Cryptography by S. Goldwasser and M. Bellare, page 18) I fail to understand what exactly does this \$ sign mean. This has been put here without any explanation or further elaboration. It may be very trivial or may be very silly of me asking it like this, but I want to understand what is means. Google search _(function, dollar, arrow)_ has not returned any result. < does not mention anything as well.

It is not standard notation as far as I know. I searched for dollar signs in the document, and found that he defines the notation 45 pages later on page 63.