Data commit

Task/Queue-Usage/CoffeeScript/queue-usage-1.coffee

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+# We build a Queue on top of an ordinary JS array, which supports push
+# and shift.  For simple queues, it might make sense to just use arrays
+# directly, but this code shows how to encapsulate the array behind a restricted
+# API.  For very large queues, you might want a more specialized data
+# structure to implement the queue, in case arr.shift works in O(N) time, which
+# is common for array implementations.  On my laptop I start noticing delay
+# after about 100,000 elements, using node.js.
+Queue = ->
+  arr = []
+  enqueue: (elem) ->
+    arr.push elem
+  dequeue: (elem) ->
+    throw Error("queue is empty") if arr.length == 0
+    arr.shift elem
+  is_empty: (elem) ->
+    arr.length == 0
+
+# test
+do ->
+  q = Queue()
+  for i in [1..100000]
+    q.enqueue i
+
+  console.log q.dequeue() # 1
+  while !q.is_empty()
+    v = q.dequeue()
+  console.log v # 1000
+
+  try
+    q.dequeue() # throws Error
+  catch e
+    console.log "#{e}"

Task/Queue-Usage/CoffeeScript/queue-usage-2.coffee

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+> coffee queue.coffee
+1
+100000
+Error: queue is empty