From 070a1d7e169bf33710e857de27c771ebdf10f3ab Mon Sep 17 00:00:00 2001
From: skilchen <skilchen@users.noreply.github.com>
Date: Sat, 21 Jul 2018 19:51:14 +0200
Subject: [PATCH] add sets.pop procedure (analogue to python) (#8383)

---
 lib/pure/collections/sets.nim | 12 ++++++++++++
 tests/sets/tsetpop.nim        | 22 ++++++++++++++++++++++
 2 files changed, 34 insertions(+)
 create mode 100644 tests/sets/tsetpop.nim

diff --git a/lib/pure/collections/sets.nim b/lib/pure/collections/sets.nim
index 59c90bc2ba85e..fdc3b4b03aa8f 100644
--- a/lib/pure/collections/sets.nim
+++ b/lib/pure/collections/sets.nim
@@ -347,6 +347,18 @@ proc excl*[A](s: var HashSet[A], other: HashSet[A]) =
   assert other.isValid, "The set `other` needs to be initialized."
   for item in other: discard exclImpl(s, item)
 
+proc pop*[A](s: var HashSet[A]): A =
+  ## Remove and return an arbitrary element from the set `s`.
+  ##
+  ## Raises KeyError if the set `s` is empty.
+  ##
+  for h in 0..high(s.data):
+    if isFilled(s.data[h].hcode):
+      result = s.data[h].key
+      excl(s, result)
+      return result
+  raise newException(KeyError, "set is empty")
+
 proc containsOrIncl*[A](s: var HashSet[A], key: A): bool =
   ## Includes `key` in the set `s` and tells if `key` was added to `s`.
   ##
diff --git a/tests/sets/tsetpop.nim b/tests/sets/tsetpop.nim
new file mode 100644
index 0000000000000..c37bda57d9fbf
--- /dev/null
+++ b/tests/sets/tsetpop.nim
@@ -0,0 +1,22 @@
+discard """
+  targets: "c c++ js"
+  output: '''1000
+0
+set is empty
+'''
+"""
+
+import sets
+
+var a = initSet[int]()
+for i in 1..1000:
+  a.incl(i)
+echo len(a)
+for i in 1..1000:  
+  discard a.pop()
+echo len(a)
+
+try:
+  echo a.pop()
+except KeyError as e:
+  echo e.msg
\ No newline at end of file