FAIC: CPS Revisited

Eric Lippert of Fabulous Adventures In Coding has posted a series on CPS tranformation and different control flow abstractions. Good stuff — recommended reading for translating the crazy stuff I talk about into ‘normal’ code.

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GOTOs inconvenient

From “The Discovery of Continuations

The talk actually had one direct and important consequence for computing. Under the inspiration of the notion of the unnecessity of goto’s, Dijkstra spent that evening constructing realistic examples of programs without goto’s, … So while van Wijngaarden said that goto’s were unnecessary … , Dijkstra stretched the point to say that goto’s were inconvenient. The latter lesson stuck. — McIlroy

The continuation passing transformation grew out an attempt to formalize GOTO, and ended up both obsoleting it as well as producing new, better structured control primitives (for example, break).  It’s strange to me that I could have gone as far as I have, as a programmer, without having a good understanding of this concept. We use it implicitly all the time — the call stack of course — but rarely consider all of the ramifications (threading) and certainly not all of the utility (coroutines, exception handling, etc).