Created
September 3, 2012 14:48
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In the smallest possible Coffeescript code, chain an array of async callbacks to "thread" their evaluation order. Inspired from Haskell
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# this should do the same thing with less code by using the array of functions as a LIFO stack | |
exec_cb_stack = (stack) => | |
cb = () => | |
stack.pop() cb if stack.length | |
stack.pop() cb | |
# | |
# example usage | |
# | |
final_fn = () -> alert('goodbye') | |
other_fns = [] | |
iters = ['greetings','how do you do?'] | |
for i in iters | |
other_fns.push ((cb)-> alert(iters.shift()); cb()) | |
exec_cb_stack [final_fn].concat(other_fns) |
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# Construct a chained array of callbacks that "thread" a sequence of async functions in the smallest possible code. | |
# tldr; call the next async function in fn, "wait" for its callback to store the result and call the next async callback in cb | |
# each async function | |
# accepts 1 callback argument | |
# passes 1 arg of result data to the callback | |
# construct the callback | |
# when callback in cb evaluates, replaces itself in cb array with the result | |
# calls the next callback in cb | |
# after last callback in cb, return joined results stored in cb | |
monadik = (fn,fnend) -> | |
cb = [] | |
(f = (k) -> | |
if k isnt fn.length | |
k1 = k+1 | |
cb[k] = (d) -> | |
cb[k] = d | |
if k1 is fn.length then fnend(cb) | |
else fn[k1] (d) -> cb[k1](d) | |
f k1)(0) | |
fn[0] cb[0] | |
monadik [some_async_fn1, some_async_fn2], (res) -> | |
console.log "monadik done res "+res |
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