call/cc in Lua - Possible?

Question

The Wikipedia article on Continuation says:
\"In any language which supports closures, it is possible to write programs in continuation passing style an

Answer 1

There are two prerequisites to manually implement call/cc per the Wikipedia quote:

1. the language must support closures
2. you must write your program in continuation passing style (CPS)

I suspect you will not like #2.

To write your program in continuation passing style:

1. Every function must take a continuation argument
2. Functions must return by calling their continuation

So, using k as the name of the continuation argument, a function would look like:

function multiplyadd(k, x, y, z) return k(x * y + z) end

The toplevel might use print as its continuation, so invoking multiplyadd at top level would look like:

multiplyadd(print, 2, 4, 1)

With that scaffolding we could define call/cc as

function callcc(k,f) return f(k,k) end

Note that the above multiplyadd actually cheats since * and + are not in CPS. It is very tedious to add all the operators in CPS form, replace all the Lua library functions with CPS equivalents, and translate/generate all your code to CPS; see details here.