Sunday, July 31, 2011

Some history

Reading the interesting Portable and high-level access to the stack with Continuation Marks, I found the following quote about procedure calls (my emphasis):
This [not properly tail-calling] behavior of the SECD machine, and more broadly of many compilers and evaluators, is principally a consequence of the early evolution of computers and computer languages; procedure calls, and particularly recursive procedure calls, were added to many computer languages long after constructs like branches, jumps, and assignment. They were thought to be expensive, inefficient, and esoteric.

Guy Steele outlined this history and disrupted the canard of expensive procedure calls, showing how inefficient procedure call mechanisms could be replaced with simple “JUMP” instructions, making the space complexity of recursive procedures equivalent to that of any other looping construct.
Then it gets highly ironic, with a quote by Alan Kay:
Though OOP came from many motivations, two were central. ... [T]he small scale one was to find a more flexible version of assignment, and then to try to eliminate it altogether.

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