[orclev]

Sadly yes, yes I have. One of the very first professional projects I worked on was a system to replace an Excel spreadsheet because they were having issues with locks when trying to concurrently modify it on their network share. The project requirements where literally "implement what Excel does", and the answer to any question about the program behavior was "What does Excel do? Do that". On the one hand it was wonderfully simple and a great opportunity to play around with Backus-Nauer forms and the guts of an interpreter. On the other hand spending months re-implementing Excel rather than solving the actual problem was rather soul destroying.