add a note on when to use foreach instead of map

NEWS for `foreach` [ci skip]
jiahao · Oct 26, 2015 · 71fc3b3 · 71fc3b3
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diff --git a/NEWS.md b/NEWS.md
@@ -61,6 +61,9 @@ Library improvements
  appropriate. The `sparsevec` function returns a one-dimensional sparse
  vector instead of a one-column sparse matrix. ([#13440])
 
+ * New `foreach` function for calling a function on every element of a collection when
+ the results are not needed.
+
 Deprecated or removed
 ---------------------
 

diff --git a/base/abstractarray.jl b/base/abstractarray.jl
@@ -1142,6 +1142,8 @@ doc"""
 
 Call function `f` on each element of iterable `c`.
 For multiple iterable arguments, `f` is called elementwise.
+`foreach` should be used instead of `map` when the results of `f` are not
+needed, for example in `foreach(println, array)`.
 """
 foreach(f) = (f(); nothing)
 foreach(f, itr) = (for x in itr; f(x); end; nothing)