Improve documentation for deques (#16589)

lib/pure/collections/deques.nim

@@ -7,25 +7,24 @@
 #    distribution, for details about the copyright.
 #
 
-## Implementation of a `deque`:idx: (double-ended queue).
+## An implementation of a `deque`:idx: (double-ended queue).
-## The underlying implementation uses a ``seq``.
+## The underlying implementation uses a `seq`.
 ##
-## None of the procs that get an individual value from the deque can be used
+## Note that none of the procs that get an individual value from the deque should be used
 ## on an empty deque.
-## If compiled with `boundChecks` option, those procs will raise an `IndexDefect`
+## If compiled with the `boundChecks` option, those procs will raise an `IndexDefect`
 ## on such access. This should not be relied upon, as `-d:danger` or `--checks:off` will
-## disable those checks and may return garbage or crash the program.
+## disable those checks and then the procs may return garbage or crash the program.
 ##
 ## As such, a check to see if the deque is empty is needed before any
 ## access, unless your program logic guarantees it indirectly.
 
 runnableExamples:
-  var a = initDeque[int]()
+  var a = [10, 20, 30, 40].toDeque
 
-  doAssertRaises(IndexDefect, echo a[0])
+  doAssertRaises(IndexDefect, echo a[4])
 
-  for i in 1 .. 5:
+  a.addLast(50)
-    a.addLast(10*i)
   assert $a == "[10, 20, 30, 40, 50]"
 
   assert a.peekFirst == 10
@@ -44,7 +43,8 @@ runnableExamples:
   a.shrink(fromFirst = 1, fromLast = 2)
   assert $a == "[22, 11, 20]"
 
-## **See also:**
+## See also
+## ========
 ## * `lists module <lists.html>`_ for singly and doubly linked lists and rings
 ## * `channels module <channels.html>`_ for inter-thread communication
 
@@ -54,9 +54,10 @@ import math
 
 type
   Deque*[T] = object
-    ## A double-ended queue backed with a ringed seq buffer.
+    ## A double-ended queue backed with a ringed `seq` buffer.
     ##
-    ## To initialize an empty deque use `initDeque proc <#initDeque,int>`_.
+    ## To initialize an empty deque,
+    ## use the `initDeque proc <#initDeque,int>`_.
     data: seq[T]
     head, tail, count, mask: int
 
@@ -65,7 +66,7 @@ const
 
 template initImpl(result: typed, initialSize: int) =
   let correctSize = nextPowerOfTwo(initialSize)
-  result.mask = correctSize-1
+  result.mask = correctSize - 1
   newSeq(result.data, correctSize)
 
 template checkIfInitialized(deq: typed) =
@@ -73,27 +74,27 @@ template checkIfInitialized(deq: typed) =
     if deq.mask == 0:
       initImpl(deq, defaultInitialSize)
 
-proc initDeque*[T](initialSize: int = 4): Deque[T] =
+proc initDeque*[T](initialSize: int = defaultInitialSize): Deque[T] =
   ## Creates a new empty deque.
   ##
   ## Optionally, the initial capacity can be reserved via `initialSize`
-  ## as a performance optimization.
+  ## as a performance optimization
+  ## (default: `defaultInitialSize <#defaultInitialSize>`_).
   ## The length of a newly created deque will still be 0.
   ##
-  ## See also:
+  ## **See also:**
   ## * `toDeque proc <#toDeque,openArray[T]>`_
   result.initImpl(initialSize)
 
 proc toDeque*[T](x: openArray[T]): Deque[T] {.since: (1, 3).} =
   ## Creates a new deque that contains the elements of `x` (in the same order).
   ##
-  ## See also:
+  ## **See also:**
   ## * `initDeque proc <#initDeque,int>`_
   runnableExamples:
-    var a = toDeque([7, 8, 9])
+    let a = toDeque([7, 8, 9])
     assert len(a) == 3
-    assert a.popFirst == 7
+    assert $a == "[7, 8, 9]"
-    assert len(a) == 2
 
   result.initImpl(x.len)
   for item in items(x):
@@ -120,11 +121,9 @@ template xBoundsCheck(deq, i) =
                          "Out of bounds: " & $i & " < 0")
 
 proc `[]`*[T](deq: Deque[T], i: Natural): T {.inline.} =
-  ## Accesses the i-th element of `deq`.
+  ## Accesses the `i`-th element of `deq`.
   runnableExamples:
-    var a = initDeque[int]()
+    let a = [10, 20, 30, 40, 50].toDeque
-    for i in 1 .. 5:
-      a.addLast(10*i)
     assert a[0] == 10
     assert a[3] == 40
     doAssertRaises(IndexDefect, echo a[8])
@@ -133,25 +132,20 @@ proc `[]`*[T](deq: Deque[T], i: Natural): T {.inline.} =
   return deq.data[(deq.head + i) and deq.mask]
 
 proc `[]`*[T](deq: var Deque[T], i: Natural): var T {.inline.} =
-  ## Accesses the i-th element of `deq` and return a mutable
+  ## Accesses the `i`-th element of `deq` and returns a mutable
   ## reference to it.
   runnableExamples:
-    var a = initDeque[int]()
+    var a = [10, 20, 30, 40, 50].toDeque
-    for i in 1 .. 5:
+    inc(a[0])
-      a.addLast(10*i)
+    assert a[0] == 11
-    assert a[0] == 10
-    assert a[3] == 40
-    doAssertRaises(IndexDefect, echo a[8])
 
   xBoundsCheck(deq, i)
   return deq.data[(deq.head + i) and deq.mask]
 
 proc `[]=`*[T](deq: var Deque[T], i: Natural, val: T) {.inline.} =
-  ## Changes the i-th element of `deq`.
+  ## Sets the `i`-th element of `deq` to `val`.
   runnableExamples:
-    var a = initDeque[int]()
+    var a = [10, 20, 30, 40, 50].toDeque
-    for i in 1 .. 5:
-      a.addLast(10*i)
     a[0] = 99
     a[3] = 66
     assert $a == "[99, 20, 30, 66, 50]"
@@ -161,13 +155,11 @@ proc `[]=`*[T](deq: var Deque[T], i: Natural, val: T) {.inline.} =
   deq.data[(deq.head + i) and deq.mask] = val
 
 proc `[]`*[T](deq: Deque[T], i: BackwardsIndex): T {.inline.} =
-  ## Accesses the backwards indexed i-th element.
+  ## Accesses the backwards indexed `i`-th element.
   ##
   ## `deq[^1]` is the last element.
   runnableExamples:
-    var a = initDeque[int]()
+    let a = [10, 20, 30, 40, 50].toDeque
-    for i in 1 .. 5:
-      a.addLast(10*i)
     assert a[^1] == 50
     assert a[^4] == 20
     doAssertRaises(IndexDefect, echo a[^9])
@@ -176,28 +168,24 @@ proc `[]`*[T](deq: Deque[T], i: BackwardsIndex): T {.inline.} =
   return deq[deq.len - int(i)]
 
 proc `[]`*[T](deq: var Deque[T], i: BackwardsIndex): var T {.inline.} =
-  ## Accesses the backwards indexed i-th element.
+  ## Accesses the backwards indexed `i`-th element and returns a mutable
+  ## reference to it.
   ##
   ## `deq[^1]` is the last element.
   runnableExamples:
-    var a = initDeque[int]()
+    var a = [10, 20, 30, 40, 50].toDeque
-    for i in 1 .. 5:
+    inc(a[^1])
-      a.addLast(10*i)
+    assert a[^1] == 51
-    assert a[^1] == 50
-    assert a[^4] == 20
-    doAssertRaises(IndexDefect, echo a[^9])
 
   xBoundsCheck(deq, deq.len - int(i))
   return deq[deq.len - int(i)]
 
 proc `[]=`*[T](deq: var Deque[T], i: BackwardsIndex, x: T) {.inline.} =
-  ## Changes the backwards indexed i-th element.
+  ## Sets the backwards indexed `i`-th element of `deq` to `x`.
   ##
   ## `deq[^1]` is the last element.
   runnableExamples:
-    var a = initDeque[int]()
+    var a = [10, 20, 30, 40, 50].toDeque
-    for i in 1 .. 5:
-      a.addLast(10*i)
     a[^1] = 99
     a[^3] = 77
     assert $a == "[10, 20, 77, 40, 99]"
@@ -208,14 +196,15 @@ proc `[]=`*[T](deq: var Deque[T], i: BackwardsIndex, x: T) {.inline.} =
 
 iterator items*[T](deq: Deque[T]): T =
   ## Yields every element of `deq`.
+  ##
+  ## **See also:**
+  ## * `mitems iterator <#mitems,Deque[T]>`_
   runnableExamples:
-    var a = initDeque[int]()
+    from sequtils import toSeq
-    for i in 1 .. 3:
+
-      a.addLast(10*i)
+    let a = [10, 20, 30, 40, 50].toDeque
-    from sugar import collect
+    assert toSeq(a.items) == @[10, 20, 30, 40, 50]
-    doAssert collect(for x in a: x) == [10, 20, 30]
+
-    # same as above:
-    doAssert collect(for x in items(a): x) == [10, 20, 30]
   var i = deq.head
   for c in 0 ..< deq.count:
     yield deq.data[i]
@@ -223,13 +212,14 @@ iterator items*[T](deq: Deque[T]): T =
 
 iterator mitems*[T](deq: var Deque[T]): var T =
   ## Yields every element of `deq`, which can be modified.
+  ##
+  ## **See also:**
+  ## * `items iterator <#items,Deque[T]>`_
   runnableExamples:
-    var a = initDeque[int]()
+    var a = [10, 20, 30, 40, 50].toDeque
-    for i in 1 .. 5:
-      a.addLast(10*i)
     assert $a == "[10, 20, 30, 40, 50]"
     for x in mitems(a):
-      x = 5*x - 1
+      x = 5 * x - 1
     assert $a == "[49, 99, 149, 199, 249]"
 
   var i = deq.head
@@ -238,13 +228,13 @@ iterator mitems*[T](deq: var Deque[T]): var T =
     i = (i + 1) and deq.mask
 
 iterator pairs*[T](deq: Deque[T]): tuple[key: int, val: T] =
-  ## Yields every (position, value) of `deq`.
+  ## Yields every `(position, value)`-pair of `deq`.
   runnableExamples:
-    var a = initDeque[int]()
+    from sequtils import toSeq
-    for i in 1 .. 3:
+
-      a.addLast(10*i)
+    let a = [10, 20, 30].toDeque
-    from sugar import collect
+    assert toSeq(a.pairs) == @[(0, 10), (1, 20), (2, 30)]
-    doAssert collect(for k, v in pairs(a): (k, v)) == @[(0, 10), (1, 20), (2, 30)]
+
   var i = deq.head
   for c in 0 ..< deq.count:
     yield (c, deq.data[i])
@@ -253,13 +243,14 @@ iterator pairs*[T](deq: Deque[T]): tuple[key: int, val: T] =
 proc contains*[T](deq: Deque[T], item: T): bool {.inline.} =
   ## Returns true if `item` is in `deq` or false if not found.
   ##
-  ## Usually used via the ``in`` operator.
+  ## Usually used via the `in` operator.
-  ## It is the equivalent of ``deq.find(item) >= 0``.
+  ## It is the equivalent of `deq.find(item) >= 0`.
   runnableExamples:
-    var q = [7, 9].toDeque
+    let q = [7, 9].toDeque
     assert 7 in q
-    assert q.contains 7
+    assert q.contains(7)
     assert 8 notin q
+
   for e in deq:
     if e == item: return true
   return false
@@ -280,18 +271,14 @@ proc expandIfNeeded[T](deq: var Deque[T]) =
     deq.head = 0
 
 proc addFirst*[T](deq: var Deque[T], item: T) =
-  ## Adds an `item` to the beginning of the `deq`.
+  ## Adds an `item` to the beginning of `deq`.
   ##
-  ## See also:
+  ## **See also:**
   ## * `addLast proc <#addLast,Deque[T],T>`_
-  ## * `peekFirst proc <#peekFirst,Deque[T]>`_
-  ## * `peekLast proc <#peekLast,Deque[T]>`_
-  ## * `popFirst proc <#popFirst,Deque[T]>`_
-  ## * `popLast proc <#popLast,Deque[T]>`_
   runnableExamples:
     var a = initDeque[int]()
     for i in 1 .. 5:
-      a.addFirst(10*i)
+      a.addFirst(10 * i)
     assert $a == "[50, 40, 30, 20, 10]"
 
   expandIfNeeded(deq)
@@ -300,18 +287,14 @@ proc addFirst*[T](deq: var Deque[T], item: T) =
   deq.data[deq.head] = item
 
 proc addLast*[T](deq: var Deque[T], item: T) =
-  ## Adds an `item` to the end of the `deq`.
+  ## Adds an `item` to the end of `deq`.
   ##
-  ## See also:
+  ## **See also:**
   ## * `addFirst proc <#addFirst,Deque[T],T>`_
-  ## * `peekFirst proc <#peekFirst,Deque[T]>`_
-  ## * `peekLast proc <#peekLast,Deque[T]>`_
-  ## * `popFirst proc <#popFirst,Deque[T]>`_
-  ## * `popLast proc <#popLast,Deque[T]>`_
   runnableExamples:
     var a = initDeque[int]()
     for i in 1 .. 5:
-      a.addLast(10*i)
+      a.addLast(10 * i)
     assert $a == "[10, 20, 30, 40, 50]"
 
   expandIfNeeded(deq)
@@ -322,16 +305,11 @@ proc addLast*[T](deq: var Deque[T], item: T) =
 proc peekFirst*[T](deq: Deque[T]): T {.inline.} =
   ## Returns the first element of `deq`, but does not remove it from the deque.
   ##
-  ## See also:
+  ## **See also:**
-  ## * `addFirst proc <#addFirst,Deque[T],T>`_
+  ## * `peekFirst proc <#peekFirst,Deque[T]_2>`_ which returns a mutable reference
-  ## * `addLast proc <#addLast,Deque[T],T>`_
   ## * `peekLast proc <#peekLast,Deque[T]>`_
-  ## * `popFirst proc <#popFirst,Deque[T]>`_
-  ## * `popLast proc <#popLast,Deque[T]>`_
   runnableExamples:
-    var a = initDeque[int]()
+    let a = [10, 20, 30, 40, 50].toDeque
-    for i in 1 .. 5:
-      a.addLast(10*i)
     assert $a == "[10, 20, 30, 40, 50]"
     assert a.peekFirst == 10
     assert len(a) == 5
@@ -342,16 +320,11 @@ proc peekFirst*[T](deq: Deque[T]): T {.inline.} =
 proc peekLast*[T](deq: Deque[T]): T {.inline.} =
   ## Returns the last element of `deq`, but does not remove it from the deque.
   ##
-  ## See also:
+  ## **See also:**
-  ## * `addFirst proc <#addFirst,Deque[T],T>`_
+  ## * `peekLast proc <#peekLast,Deque[T]_2>`_ which returns a mutable reference
-  ## * `addLast proc <#addLast,Deque[T],T>`_
   ## * `peekFirst proc <#peekFirst,Deque[T]>`_
-  ## * `popFirst proc <#popFirst,Deque[T]>`_
-  ## * `popLast proc <#popLast,Deque[T]>`_
   runnableExamples:
-    var a = initDeque[int]()
+    let a = [10, 20, 30, 40, 50].toDeque
-    for i in 1 .. 5:
-      a.addLast(10*i)
     assert $a == "[10, 20, 30, 40, 50]"
     assert a.peekLast == 50
     assert len(a) == 5
@@ -360,41 +333,31 @@ proc peekLast*[T](deq: Deque[T]): T {.inline.} =
   result = deq.data[(deq.tail - 1) and deq.mask]
 
 proc peekFirst*[T](deq: var Deque[T]): var T {.inline, since: (1, 3).} =
-  ## Returns the first element of `deq`, but does not remove it from the deque.
+  ## Returns a mutable reference to the first element of `deq`,
+  ## but does not remove it from the deque.
   ##
-  ## See also:
+  ## **See also:**
-  ## * `addFirst proc <#addFirst,Deque[T],T>`_
+  ## * `peekFirst proc <#peekFirst,Deque[T]>`_
-  ## * `addLast proc <#addLast,Deque[T],T>`_
+  ## * `peekLast proc <#peekLast,Deque[T]_2>`_
-  ## * `peekLast proc <#peekLast,Deque[T]>`_
-  ## * `popFirst proc <#popFirst,Deque[T]>`_
-  ## * `popLast proc <#popLast,Deque[T]>`_
   runnableExamples:
-    var a = initDeque[int]()
+    var a = [10, 20, 30, 40, 50].toDeque
-    for i in 1 .. 5:
+    a.peekFirst() = 99
-      a.addLast(10*i)
+    assert $a == "[99, 20, 30, 40, 50]"
-    assert $a == "[10, 20, 30, 40, 50]"
-    assert a.peekFirst == 10
-    assert len(a) == 5
 
   emptyCheck(deq)
   result = deq.data[deq.head]
 
 proc peekLast*[T](deq: var Deque[T]): var T {.inline, since: (1, 3).} =
-  ## Returns the last element of `deq`, but does not remove it from the deque.
+  ## Returns a mutable reference to the last element of `deq`,
+  ## but does not remove it from the deque.
   ##
-  ## See also:
+  ## **See also:**
-  ## * `addFirst proc <#addFirst,Deque[T],T>`_
+  ## * `peekFirst proc <#peekFirst,Deque[T]_2>`_
-  ## * `addLast proc <#addLast,Deque[T],T>`_
+  ## * `peekLast proc <#peekLast,Deque[T]>`_
-  ## * `peekFirst proc <#peekFirst,Deque[T]>`_
-  ## * `popFirst proc <#popFirst,Deque[T]>`_
-  ## * `popLast proc <#popLast,Deque[T]>`_
   runnableExamples:
-    var a = initDeque[int]()
+    var a = [10, 20, 30, 40, 50].toDeque
-    for i in 1 .. 5:
+    a.peekLast() = 99
-      a.addLast(10*i)
+    assert $a == "[10, 20, 30, 40, 99]"
-    assert $a == "[10, 20, 30, 40, 50]"
-    assert a.peekLast == 50
-    assert len(a) == 5
 
   emptyCheck(deq)
   result = deq.data[(deq.tail - 1) and deq.mask]
@@ -406,17 +369,10 @@ proc popFirst*[T](deq: var Deque[T]): T {.inline, discardable.} =
   ## Removes and returns the first element of the `deq`.
   ##
   ## See also:
-  ## * `addFirst proc <#addFirst,Deque[T],T>`_
-  ## * `addLast proc <#addLast,Deque[T],T>`_
-  ## * `peekFirst proc <#peekFirst,Deque[T]>`_
-  ## * `peekLast proc <#peekLast,Deque[T]>`_
   ## * `popLast proc <#popLast,Deque[T]>`_
-  ## * `clear proc <#clear,Deque[T]>`_
   ## * `shrink proc <#shrink,Deque[T],int,int>`_
   runnableExamples:
-    var a = initDeque[int]()
+    var a = [10, 20, 30, 40, 50].toDeque
-    for i in 1 .. 5:
-      a.addLast(10*i)
     assert $a == "[10, 20, 30, 40, 50]"
     assert a.popFirst == 10
     assert $a == "[20, 30, 40, 50]"
@@ -430,18 +386,11 @@ proc popFirst*[T](deq: var Deque[T]): T {.inline, discardable.} =
 proc popLast*[T](deq: var Deque[T]): T {.inline, discardable.} =
   ## Removes and returns the last element of the `deq`.
   ##
-  ## See also:
+  ## **See also:**
-  ## * `addFirst proc <#addFirst,Deque[T],T>`_
-  ## * `addLast proc <#addLast,Deque[T],T>`_
-  ## * `peekFirst proc <#peekFirst,Deque[T]>`_
-  ## * `peekLast proc <#peekLast,Deque[T]>`_
   ## * `popFirst proc <#popFirst,Deque[T]>`_
-  ## * `clear proc <#clear,Deque[T]>`_
   ## * `shrink proc <#shrink,Deque[T],int,int>`_
   runnableExamples:
-    var a = initDeque[int]()
+    var a = [10, 20, 30, 40, 50].toDeque
-    for i in 1 .. 5:
-      a.addLast(10*i)
     assert $a == "[10, 20, 30, 40, 50]"
     assert a.popLast == 50
     assert $a == "[10, 20, 30, 40]"
@@ -455,14 +404,11 @@ proc popLast*[T](deq: var Deque[T]): T {.inline, discardable.} =
 proc clear*[T](deq: var Deque[T]) {.inline.} =
   ## Resets the deque so that it is empty.
   ##
-  ## See also:
+  ## **See also:**
-  ## * `clear proc <#clear,Deque[T]>`_
   ## * `shrink proc <#shrink,Deque[T],int,int>`_
   runnableExamples:
-    var a = initDeque[int]()
+    var a = [10, 20, 30, 40, 50].toDeque
-    for i in 1 .. 5:
+    assert $a == "[10, 20, 30, 40, 50]"
-      a.addFirst(10*i)
-    assert $a == "[50, 40, 30, 20, 10]"
     clear(a)
     assert len(a) == 0
 
@@ -477,15 +423,15 @@ proc shrink*[T](deq: var Deque[T], fromFirst = 0, fromLast = 0) =
   ## If the supplied number of elements exceeds the total number of elements
   ## in the deque, the deque will remain empty.
   ##
-  ## See also:
+  ## **See also:**
   ## * `clear proc <#clear,Deque[T]>`_
+  ## * `popFirst proc <#popFirst,Deque[T]>`_
+  ## * `popLast proc <#popLast,Deque[T]>`_
   runnableExamples:
-    var a = initDeque[int]()
+    var a = [10, 20, 30, 40, 50].toDeque
-    for i in 1 .. 5:
+    assert $a == "[10, 20, 30, 40, 50]"
-      a.addFirst(10*i)
-    assert $a == "[50, 40, 30, 20, 10]"
     a.shrink(fromFirst = 2, fromLast = 1)
-    assert $a == "[30, 20]"
+    assert $a == "[30, 40]"
 
   if fromFirst + fromLast > deq.count:
     clear(deq)
@@ -503,6 +449,10 @@ proc shrink*[T](deq: var Deque[T], fromFirst = 0, fromLast = 0) =
 
 proc `$`*[T](deq: Deque[T]): string =
   ## Turns a deque into its string representation.
+  runnableExamples:
+    let a = [10, 20, 30].toDeque
+    assert $a == "[10, 20, 30]"
+
   result = "["
   for x in deq:
     if result.len > 1: result.add(", ")