patch 7.4.2120
Problem: User defined functions can't be a closure.
Solution: Add the "closure" argument. Allow using :unlet on a bound
variable. (Yasuhiro Matsumoto, Ken Takata)
diff --git a/runtime/doc/eval.txt b/runtime/doc/eval.txt
index 196e71c..8dfbb3a 100644
--- a/runtime/doc/eval.txt
+++ b/runtime/doc/eval.txt
@@ -1240,6 +1240,7 @@
:let Bar = Foo(4)
:echo Bar(6)
< 5
+See also |:func-closure|.
Examples for using a lambda expression with |sort()|, |map()| and |filter()|: >
:echo map([1, 2, 3], {idx, val -> val + 1})
@@ -8217,7 +8218,7 @@
See |:verbose-cmd| for more information.
*E124* *E125* *E853* *E884*
-:fu[nction][!] {name}([arguments]) [range] [abort] [dict]
+:fu[nction][!] {name}([arguments]) [range] [abort] [dict] [closure]
Define a new function by the name {name}. The name
must be made of alphanumeric characters and '_', and
must start with a capital or "s:" (see above). Note
@@ -8260,6 +8261,28 @@
be invoked through an entry in a |Dictionary|. The
local variable "self" will then be set to the
dictionary. See |Dictionary-function|.
+ *:func-closure* *E932*
+ When the [closure] argument is added, the function
+ can access variables and arguments from the outer
+ scope. This is usually called a closure. In this
+ example Bar() uses "x" from the scope of Foo(). It
+ remains referenced even after Foo() returns: >
+ :function! Foo()
+ : let x = 0
+ : function! Bar() closure
+ : let x += 1
+ : return x
+ : endfunction
+ : return function('Bar')
+ :endfunction
+
+ :let F = Foo()
+ :echo F()
+< 1 >
+ :echo F()
+< 2 >
+ :echo F()
+< 3
*function-search-undo*
The last used search pattern and the redo command "."