Move sortByIt to algorithm module and add an example for it

lib/pure/algorithm.nim

@@ -194,6 +194,27 @@ proc sorted*[T](a: openArray[T], cmp: proc(x, y: T): int {.closure.}, order = So
     result[i] = a[i]
   sort(result, cmp, order)
 
+template sortByIt*(seq1, op: expr): expr =
+  ## Convenience template around the ``sorted`` proc to reduce typing.
+  ##
+  ## The template injects the ``it`` variable which you can use directly in an
+  ## expression. Example:
+  ##
+  ## .. code-block:: nim
+  ##
+  ##     var users: seq[tuple[id: int, name: string]] =
+  ##       @[(0, "Smith"), (1, "Pratt"), (2, "Sparrow")]
+  ##
+  ##     echo users.sortByIt(it.name)
+  ##
+  var result {.gensym.} = sorted(seq1, proc(x, y: type(seq1[0])): int =
+    var it {.inject.} = x
+    let a = op
+    it = y
+    let b = op
+    result = cmp(a, b))
+  result
+
 proc product*[T](x: openArray[seq[T]]): seq[seq[T]] =
   ## produces the Cartesian product of the array. Warning: complexity
   ## may explode.

lib/pure/collections/sequtils.nim

@@ -26,8 +26,6 @@
 when not defined(nimhygiene):
   {.pragma: dirty.}
 
-import algorithm
-
 proc concat*[T](seqs: varargs[seq[T]]): seq[T] =
   ## Takes several sequences' items and returns them inside a new sequence.
   ##
@@ -417,19 +415,6 @@ template mapIt*(varSeq, op: expr) =
     let it {.inject.} = varSeq[i]
     varSeq[i] = op
 
-template sortByIt*(seq1, op: expr): expr =
-  ## Convenience template around the ``sorted`` proc to reduce typing.
-  ##
-  ## The template injects the ``it`` variable which you can use directly in an
-  ## expression.
-  var result {.gensym.} = sorted(seq1, proc(x, y: type(seq1[0])): int =
-    var it {.inject.} = x
-    let a = op
-    it = y
-    let b = op
-    result = cmp(a, b))
-  result
-
 template newSeqWith*(len: int, init: expr): expr =
   ## creates a new sequence, calling `init` to initialize each value. Example:
   ##