repeat , for etc. are parts of a language that the parser gives high priority to in this case, R thinks that you are going to write something that he needed to evaluate before calling the function ?() as a result. The canonical solution is to specify the name of the function using backlinks:
?`repeat`
As DWin notes above, this can be used for any function name. Backticks are also useful for quoting objects or components of lists / data frames that have non-standard names.
Gavin simpson
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