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#
#
# Nim's Runtime Library
# (c) Copyright 2012 Andreas Rumpf
#
# See the file "copying.txt", included in this
# distribution, for details about the copyright.
#
## Implementation of a `queue`:idx:. The underlying implementation uses a ``seq``.
## Note: For inter thread communication use
## a `Channel <channels.html>`_ instead.
proc englishOrdinal(n: SomeInteger): string =
# Temporary proc. Needs to be moved somewhere else as it can be reused in
# other places too.
# If this accepted number strings instead and only gave out the letters it
# would be more flexible, permitting things like 1.100.000th, 34,545,321st
# but it would be harder and more error prone to use.
let num = $n
if num.len > 1 and num[^2] == '1':
return num & "th"
else:
case num[^1]
of '1': return num & "st"
of '2': return num & "nd"
of '3': return num & "rd"
else: return num & "th"
import math
type
Queue*[T] = object ## a queue
data: seq[T]
rd, wr, count, mask: int
{.deprecated: [TQueue: Queue].}
proc initQueue*[T](initialSize: int = 4): Queue[T] =
## creates a new queue. `initialSize` needs to be a power of 2.
assert isPowerOfTwo(initialSize)
result.mask = initialSize-1
newSeq(result.data, initialSize)
proc len*[T](q: Queue[T]): int {.inline.}=
## returns the number of elements of `q`.
result = q.count
proc low*[T](q: Queue[T]): int {.inline.}=
## returns the index of the oldest element of `q` (always 0).
result = 0
proc high*[T](q: Queue[T]): int {.inline.}=
## returns the index of the last element inserted on `q` (equivalent to
## `q.len - 1`).
result = q.count - 1
proc front*[T](q: Queue[T]): T {.inline.}=
## returns the oldest element of `q`. Equivalent to `q.pop()` but does not
## remove it from the queue.
assert q.count > 0
result = q.data[q.rd]
proc back*[T](q: Queue[T]): T {.inline.} =
## returns the newest element of `q` but does not remove it from the queue.
assert q.count > 0
result = q.data[q.wr - 1]
template xBoundsCheck(q, i) =
# Bounds check for the array like acceses.
when compileOption("boundChecks"): # d:release should disable this.
if i > q.high: # x < q.low is taken care by the Natural parameter
raise newException(IndexError,
"You tried to access the " & englishOrdinal(i+1) &
" element of the queue but it has only " &
$q.len & " elements.")
discard
proc `[]`*[T](q: Queue[T], i: Natural) : T {.inline.} =
## Acess the i-th element of `q` by order of insertion.
## q[0] is the oldest (the next one q.pop() will extract),
## q[^1] is the newest (last one added to the queue).
xBoundsCheck(q, i)
return q.data[q.rd + i and q.mask]
proc `[]`*[T](q: var Queue[T], i: Natural): var T {.inline.} =
## Acess the i-th element of `q` and returns a mutable
## reference to it.
xBoundsCheck(q, i)
return q.data[q.rd + i and q.mask]
proc `[]=`* [T] (q: var Queue[T], i: Natural, val : T) {.inline.} =
## Change the i-th element of `q`.
xBoundsCheck(q, i)
q.data[q.rd + i and q.mask] = val
iterator items*[T](q: Queue[T]): T =
## yields every element of `q`.
var i = q.rd
for c in 0 ..< q.count:
yield q.data[i]
i = (i + 1) and q.mask
iterator mitems*[T](q: var Queue[T]): var T =
## yields every element of `q`.
var i = q.rd
for c in 0 ..< q.count:
yield q.data[i]
i = (i + 1) and q.mask
iterator pairs*[T](q: Queue[T]): tuple[key: int, val: T] =
## yields every (position, value) of `q`.
var i = q.rd
for c in 0 ..< q.count:
yield (c, q.data[i])
i = (i + 1) and q.mask
proc contains*[T](q: Queue[T], item: T): bool {.inline.} =
## Returns true if `item` is in `q` or false if not found. Usually used
## via the ``in`` operator. It is the equivalent of ``q.find(item) >= 0``.
##
## .. code-block:: Nim
## if x in q:
## assert q.contains x
for e in q:
if e == item: return true
return false
proc add*[T](q: var Queue[T], item: T) =
## adds an `item` to the end of the queue `q`.
var cap = q.mask+1
if q.count >= cap:
var n {.noinit.} = newSeq[T](cap*2)
for i, x in q:
shallowCopy(n[i], x) # does not use copyMem because the GC.
shallowCopy(q.data, n)
q.mask = cap*2 - 1
q.wr = q.count
q.rd = 0
inc q.count
q.data[q.wr] = item
q.wr = (q.wr + 1) and q.mask
proc pop*[T](q: var Queue[T]): T =
## removes and returns the first (oldest) element of the queue `q`.
assert q.count > 0
dec q.count
result = q.data[q.rd]
q.rd = (q.rd + 1) and q.mask
proc enqueue*[T](q: var Queue[T], item: T) =
## alias for the ``add`` operation.
q.add(item)
proc dequeue*[T](q: var Queue[T]): T =
## alias for the ``pop`` operation.
q.pop()
proc `$`*[T](q: Queue[T]): string =
## turns a queue into its string representation.
result = "["
for x in q:
if result.len > 1: result.add(", ")
result.add($x)
result.add("]")
when isMainModule:
var q = initQueue[int]()
q.add(123)
q.add(9)
q.enqueue(4)
var first = q.dequeue()
q.add(56)
q.add(6)
var second = q.pop()
q.add(789)
assert first == 123
assert second == 9
assert($q == "[4, 56, 6, 789]")
assert q[0] == q.front and q.front == 4
assert q[^1] == q.back and q.back == 789
q[0] = 42
q[^1] = 7
assert q[q.low] == 42
assert q[q.high] == 7
assert 6 in q and 789 notin q
assert q.find(6) >= 0
assert q.find(789) < 0
for i in -2 .. 10:
if i in q:
assert q.contains(i) and q.find(i) >= 0
else:
assert(not q.contains(i) and q.find(i) < 0)
when compileOption("boundChecks"):
try:
echo q[99]
assert false
except IndexError:
discard
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