Adds documentation examples to sequtils.

lib/pure/collections/sequtils.nim

@@ -15,6 +15,11 @@
 ## sequence, it already exists as the `each` proc in the `system
 ## <system.html>`_ module in both mutable and immutable styles.
 ##
+## Also, for functional style programming you may want to pass `anonymous procs
+## <manual.html#anonymous-procs>`_ to procs like ``filter`` to reduce typing.
+## Anonymous procs can use `the special do notation <manual.html#do-notation>`_
+## which is more convenient in certain situations.
+##
 ## **Note**: This interface will change as soon as the compiler supports
 ## closures and proper coroutines.
 
@@ -22,7 +27,17 @@ when not defined(nimhygiene):
   {.pragma: dirty.}
 
 proc concat*[T](seqs: varargs[seq[T]]): seq[T] =
-  ## Takes several sequences' items and returns them inside of one sequence.
+  ## Takes several sequences' items and returns them inside a new sequence.
+  ##
+  ## Example:
+  ##
+  ## .. code-block:: nimrod
+  ##   let
+  ##     s1 = @[1, 2, 3]
+  ##     s2 = @[4, 5]
+  ##     s3 = @[6, 7]
+  ##     total = concat(s1, s2, s3)
+  ##   assert total == @[1, 2, 3, 4, 5, 6, 7]
   var L = 0
   for seqitm in items(seqs): inc(L, len(seqitm))
   newSeq(result, L)
@@ -33,14 +48,38 @@ proc concat*[T](seqs: varargs[seq[T]]): seq[T] =
       inc(i)
 
 proc distnct*[T](seq1: seq[T]): seq[T] =
-  ## Removes duplicates from a sequence and returns it.
+  ## Returns a new sequence without duplicates. Example:
+  ##
+  ## .. code-block:: nimrod
+  ##   let
+  ##     dup1 = @[1, 1, 3, 4, 2, 2, 8, 1, 4]
+  ##     dup2 = @["a", "a", "c", "d", "d"]
+  ##     unique1 = distnct(dup1)
+  ##     unique2 = distnct(dup2)
+  ##   assert unique1 == @[1, 3, 4, 2, 8]
+  ##   assert unique2 == @["a", "c", "d"]
   result = @[]
   for itm in items(seq1):
     if not result.contains(itm): result.add(itm)
     
 proc zip*[S, T](seq1: seq[S], seq2: seq[T]): seq[tuple[a: S, b: T]] =
-  ## Combines two sequences. If one sequence is too short,
-  ## the remaining items in the longer sequence are discarded.
+  ## Returns a new sequence with a combination of the two input sequences.
+  ##
+  ## For convenience you can access the returned tuples through the named
+  ## fields `a` and `b`. If one sequence is shorter, the remaining items in the
+  ## longer sequence are discarded. Example:
+  ##
+  ## .. code-block:: nimrod
+  ##   let
+  ##     short = @[1, 2, 3]
+  ##     long = @[6, 5, 4, 3, 2, 1]
+  ##     words = @["one", "two", "three"]
+  ##     zip1 = zip(short, long)
+  ##     zip2 = zip(short, words)
+  ##   assert zip1 == @[(1, 6), (2, 5), (3, 4)]
+  ##   assert zip2 == @[(1, "one"), (2, "two"), (3, "three")]
+  ##   assert zip1[2].b == 4
+  ##   assert zip2[2].b == "three"
   var m = min(seq1.len, seq2.len)
   newSeq(result, m)
   for i in 0 .. m-1: result[i] = (seq1[i], seq2[i])
@@ -48,18 +87,44 @@ proc zip*[S, T](seq1: seq[S], seq2: seq[T]): seq[tuple[a: S, b: T]] =
 iterator filter*[T](seq1: seq[T], pred: proc(item: T): bool {.closure.}): T =
   ## Iterates through a sequence and yields every item that fulfills the
   ## predicate.
+  ##
+  ## Example:
+  ##
+  ## .. code-block:: nimrod
+  ##   let numbers = @[1, 4, 5, 8, 9, 7, 4]
+  ##   for n in filter(numbers, proc (x: int): bool = x mod 2 == 0):
+  ##     echo($n)
+  ##   # echoes 4, 8, 4 in separate lines
   for i in countup(0, len(seq1) -1):
     var item = seq1[i]
     if pred(item): yield seq1[i]
 
 proc filter*[T](seq1: seq[T], pred: proc(item: T): bool {.closure.}): seq[T] =
-  ## Returns all items in a sequence that fulfilled the predicate.
+  ## Returns a new sequence with all the items that fulfilled the predicate.
+  ##
+  ## Example:
+  ##
+  ## .. code-block:: nimrod
+  ##   let
+  ##     colors = @["red", "yellow", "black"]
+  ##     f1 = filter(colors, proc(x: string): bool = x.len < 6)
+  ##     f2 = filter(colors) do (x: string) -> bool : x.len > 5
+  ##   assert f1 == @["red", "black"]
+  ##   assert f2 == @["yellow"]
   accumulateResult(filter(seq1, pred))
 
 template filterIt*(seq1, pred: expr): expr {.immediate, dirty.} =
-  ## Finds a specific item in a sequence as long as the 
-  ## predicate returns true. The predicate needs to be an expression
-  ## containing ``it``: ``filterIt("abcxyz", it == 'x')``.
+  ## Returns a new sequence with all the items that fulfilled the predicate.
+  ##
+  ## Unlike the `proc` version, the predicate needs to be an expression using
+  ## the ``it`` variable for testing, like: ``filterIt("abcxyz", it == 'x')``.
+  ## Example:
+  ##
+  ## .. code-block:: nimrod
+  ##    let
+  ##      temperatures = @[-272.15, -2.0, 24.5, 44.31, 99.9, -113.44]
+  ##      acceptable = filterIt(temperatures, it < 50 and it > -10)
+  ##    assert acceptable == @[-2.0, 24.5, 44.31]
   block:
     var result: type(seq1) = @[]
     for it in items(seq1):
@@ -68,7 +133,79 @@ template filterIt*(seq1, pred: expr): expr {.immediate, dirty.} =
 
 template toSeq*(iter: expr): expr {.immediate.} =
   ## Transforms any iterator into a sequence.
+  ##
+  ## Example:
+  ##
+  ## .. code-block:: nimrod
+  ##   let
+  ##     numeric = @[1, 2, 3, 4, 5, 6, 7, 8, 9]
+  ##     odd_numbers = toSeq(filter(numeric) do (x: int) -> bool:
+  ##       if x mod 2 == 1:
+  ##         result = true)
+  ##   assert odd_numbers == @[1, 3, 5, 7, 9]
+  ##
   var result {.gensym.}: seq[type(iter)] = @[]
   for x in iter: add(result, x)
   result
 
+when isMainModule:
+  import strutils
+  proc toStr(x: int): string {.procvar.} = $x
+  # concat test
+  let
+    s1 = @[1, 2, 3]
+    s2 = @[4, 5]
+    s3 = @[6, 7]
+    total = concat(s1, s2, s3)
+  assert total == @[1, 2, 3, 4, 5, 6, 7]
+
+  # duplicates test
+  let
+    dup1 = @[1, 1, 3, 4, 2, 2, 8, 1, 4]
+    dup2 = @["a", "a", "c", "d", "d"]
+    unique1 = distnct(dup1)
+    unique2 = distnct(dup2)
+  assert unique1 == @[1, 3, 4, 2, 8]
+  assert unique2 == @["a", "c", "d"]
+
+  # zip test
+  let
+    short = @[1, 2, 3]
+    long = @[6, 5, 4, 3, 2, 1]
+    words = @["one", "two", "three"]
+    zip1 = zip(short, long)
+    zip2 = zip(short, words)
+  assert zip1 == @[(1, 6), (2, 5), (3, 4)]
+  assert zip2 == @[(1, "one"), (2, "two"), (3, "three")]
+  assert zip1[2].b == 4
+  assert zip2[2].b == "three"
+
+  # filter proc test
+  let
+    colors = @["red", "yellow", "black"]
+    f1 = filter(colors, proc(x: string): bool = x.len < 6)
+    f2 = filter(colors) do (x: string) -> bool : x.len > 5
+  assert f1 == @["red", "black"]
+  assert f2 == @["yellow"]
+
+  # filter iterator test
+  let numbers = @[1, 4, 5, 8, 9, 7, 4]
+  for n in filter(numbers, proc (x: int): bool = x mod 2 == 0):
+    echo($n)
+  # echoes 4, 8, 4 in separate lines
+
+  # filterIt test
+  let
+    temperatures = @[-272.15, -2.0, 24.5, 44.31, 99.9, -113.44]
+    acceptable = filterIt(temperatures, it < 50 and it > -10)
+  assert acceptable == @[-2.0, 24.5, 44.31]
+
+  # toSeq test
+  let
+    numeric = @[1, 2, 3, 4, 5, 6, 7, 8, 9]
+    odd_numbers = toSeq(filter(numeric) do (x: int) -> bool:
+      if x mod 2 == 1:
+        result = true)
+  assert odd_numbers == @[1, 3, 5, 7, 9]
+
+  echo "Finished doc tests"