Question: Define a function 'sleep' that behaves similarly to the Unix system command 'sleep'. The function should receive a 'time' as the input argument.
More Information:
https://en.wikipedia.org/wiki/Sleep_(command)
q)\t sleep each 1e3*1 2 5 / seconds
7999
q)\t sleep 500 / millis
499
######## solution.q ########
sleep:{st:.z.T; while[.z.T<st+x;()]}
Explanation: Store the current time in a variable, and use a while loop that does not end until the current time is greater than or equal to the stored time plus the input time.