Earlier quoted context omitted.
Closures as a form of encapsulation is actually very lispy. Simula introduced classes while Sketchpad introduced prototypes (predates Simula by 5 years), so both were very much proto OO in that sense. But if it makes you feel any better, we could define proto OO just to mean OO before that was a term anyone invented.
It's not closures I described. I don't remember if Simula even have closures or not - it's possible it does. The mechanism I described involves message passing between co-routines. In any case, I detest Simula with the kind of burning hate you can only experience after having been forced to use it (it was the language used in a compulsory CS course; though admittedly most of my hate stems from the horrible standard l…
Surely you weren't using Simula 1 or Simula 67 in your courses?