I'll explain that one. In the 1970s Burge wrote a book "Recursive Programming Techniques" explaining cool things you can do with functional programming -- yes,

I'll explain that one. In the 1970s Burge wrote a book "Recursive Programming Techniques" explaining cool things you can do with functional programming -- yes, a lot of that stuff goes back that far. Reynolds invented a functional language called Gedanken -- the paper was iirc 1972. (I don't remember if Burge used Gedanken in his book, or if it was just similar notation, both inspired by Landin. I think it was the latter and you couldn't actually run any of the code in the book.) The pun is about fluid mechanics and 'control flow'.