Merge pull request #2411 from reactormonk/merge-counttables

merge for CountTable, see #1680

lib/pure/collections/tables.nim

@@ -984,6 +984,22 @@ proc sort*[A](t: CountTableRef[A]) =
   ## `t` in the sorted order.
   t[].sort
 
+proc merge*[A](s: var CountTable[A], t: CountTable[A]) =
+  ## merges the second table into the first one
+  for key, value in t:
+    s.inc(key, value)
+
+proc merge*[A](s, t: CountTable[A]): CountTable[A] =
+  ## merges the two tables into a new one
+  result = initCountTable[A](nextPowerOfTwo(max(s.len, t.len)))
+  for table in @[s, t]:
+    for key, value in table:
+      result.inc(key, value)
+
+proc merge*[A](s, t: CountTableRef[A]) =
+  ## merges the second table into the first one
+  s[].merge(t[])
+
 when isMainModule:
   type
     Person = object
@@ -1012,3 +1028,48 @@ when isMainModule:
   s2[p2] = 45_000
   s3[p1] = 30_000
   s3[p2] = 45_000
+
+  var
+    t1 = initCountTable[string]()
+    t2 = initCountTable[string]()
+  t1.inc("foo")
+  t1.inc("bar", 2)
+  t1.inc("baz", 3)
+  t2.inc("foo", 4)
+  t2.inc("bar")
+  t2.inc("baz", 11)
+  merge(t1, t2)
+  assert(t1["foo"] == 5)
+  assert(t1["bar"] == 3)
+  assert(t1["baz"] == 14)
+
+  let
+    t1r = newCountTable[string]()
+    t2r = newCountTable[string]()
+  t1r.inc("foo")
+  t1r.inc("bar", 2)
+  t1r.inc("baz", 3)
+  t2r.inc("foo", 4)
+  t2r.inc("bar")
+  t2r.inc("baz", 11)
+  merge(t1r, t2r)
+  assert(t1r["foo"] == 5)
+  assert(t1r["bar"] == 3)
+  assert(t1r["baz"] == 14)
+
+  var
+    t1l = initCountTable[string]()
+    t2l = initCountTable[string]()
+  t1l.inc("foo")
+  t1l.inc("bar", 2)
+  t1l.inc("baz", 3)
+  t2l.inc("foo", 4)
+  t2l.inc("bar")
+  t2l.inc("baz", 11)
+  let
+    t1merging = t1l
+    t2merging = t2l
+  let merged = merge(t1merging, t2merging)
+  assert(merged["foo"] == 5)
+  assert(merged["bar"] == 3)
+  assert(merged["baz"] == 14)