User defined functions have been available as long as I can remember in Excel! Yes they must be defined in VBA and the VBA Editor feels like it has not been updated since 1980, but they are still quite easy to write and extremely powerful and useful.
These lambdas look great and a bit more accessible than opening VBA, but I don’t get why they are being hailed as some kind of revolutionary paradigm shift for Excel.
You can write anything in VBA, (the horror...the horror) and Power Query also seems to be a complete more or less functional programming language. So I believe Excel was Turing complete for almost 30 years and doubly so for a significant part of the last decade. There might be more languages lurking in there somewhere.
Seems like this is VBA macros all over again. I hope they placed some safeguards in these new lambda functions to prevent their misuse for malicious purposes (like the infected vba macro viruses of old).
`=NOT(UNSAFE(MyLambda(foo)))` should do the trick!