From def3e015c7a8c82430fff20994b75b233c0c423b Mon Sep 17 00:00:00 2001
From: Yuriy Glukhov <yutiy.glukhov@gmail.com>
Date: Mon, 27 Jun 2016 17:44:05 +0300
Subject: Added closureScope template

---
 lib/system.nim | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

(limited to 'lib')

diff --git a/lib/system.nim b/lib/system.nim
index 5a84f4a52..6a4265e5a 100644
--- a/lib/system.nim
+++ b/lib/system.nim
@@ -3633,6 +3633,27 @@ proc `==` *(x, y: cstring): bool {.magic: "EqCString", noSideEffect,
   elif x.isNil or y.isNil: result = false
   else: result = strcmp(x, y) == 0
 
+template closureScope*(body: untyped): stmt =
+  ## Useful when creating a closure in a loop to capture local loop variables by
+  ## their current iteration values. Example:
+  ##
+  ## .. code-block:: nim
+  ##   var myClosure : proc()
+  ##   # without closureScope:
+  ##   for i in 0 .. 5:
+  ##     let j = i
+  ##     if j == 3:
+  ##       myClosure = proc() = echo j
+  ##   myClosure() # outputs 5. `j` is changed after closure creation
+  ##   # with closureScope:
+  ##   for i in 0 .. 5:
+  ##     closureScope: # Everything in this scope is locked after closure creation
+  ##       let j = i
+  ##       if j == 3:
+  ##         myClosure = proc() = echo j
+  ##   myClosure() # outputs 3
+  (proc() = body)()
+
 {.pop.} #{.push warning[GcMem]: off, warning[Uninit]: off.}
 
 when defined(nimconfig):
-- 
cgit 1.4.1-2-gfad0