Merge pull request #1075 from flaviut/inlinedocs

Add some documentations and code examples in system

tests/misc/tfilter.nim

@@ -0,0 +1,41 @@
+discard """
+  output: "02468101214161820\n15"
+"""
+
+proc filter[T](list: seq[T], f: proc (item: T): bool {.closure.}): seq[T] =
+  result = @[]
+  for i in items(list):
+    if f(i):
+      result.add(i)
+
+let nums = @[0, 1, 2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20]
+
+when true:
+  let nums2 = filter(nums,
+               (proc (item: int): bool =
+                 result = (item mod 2) == 0)
+               )
+
+proc outer =
+  # lets use a proper closure this time:
+  var modulo = 2
+  let nums2 = filter(nums,
+               (proc (item: int): bool = result = (item mod modulo) == 0)
+               )
+
+  for n in nums2: stdout.write(n)
+  stdout.write("\n")
+
+outer()
+
+import math
+proc compose[T](f1, f2: proc (x: T): T {.closure.}): proc (x: T): T {.closure.} =
+  result = (proc (x: T): T =
+             result = f1(f2(x)))
+
+
+proc add5(x: int): int = result = x + 5
+
+var test = compose(add5, add5)
+echo test(5)
+