Add docs, do-block function for get

Also added get, get! for WeakKeyDicts

base/dict.jl

@@ -554,6 +554,11 @@ function get{K,V}(h::Dict{K,V}, key, deflt)
     return (index<0) ? deflt : h.vals[index]::V
 end
 
+function get{K,V}(deflt::Function, h::Dict{K,V}, key)
+    index = ht_keyindex(h, key)
+    return (index<0) ? deflt() : h.vals[index]::V
+end
+
 haskey(h::Dict, key) = (ht_keyindex(h, key) >= 0)
 in{T<:Dict}(key, v::KeyIterator{T}) = (ht_keyindex(v.dict, key) >= 0)
 
@@ -665,6 +670,9 @@ function getkey{K}(wkh::WeakKeyDict{K}, kk, deflt)
 end
 
 get{K}(wkh::WeakKeyDict{K}, key, def) = get(wkh.ht, key, def)
+get{K}(def::Function, wkh::WeakKeyDict{K}, key) = get(def, wkh.ht, key)
+get!{K}(wkh::WeakKeyDict{K}, key, def) = get!(wkh.ht, key, def)
+get!{K}(def::Function, wkh::WeakKeyDict{K}, key) = get!(def, wkh.ht, key)
 pop!{K}(wkh::WeakKeyDict{K}, key) = pop!(wkh.ht, key)
 pop!{K}(wkh::WeakKeyDict{K}, key, def) = pop!(wkh.ht, key, def)
 delete!{K}(wkh::WeakKeyDict{K}, key) = delete!(wkh.ht, key)

doc/stdlib/base.rst

@@ -727,6 +727,17 @@ Given a dictionary ``D``, the syntax ``D[x]`` returns the value of key ``x`` (if
 
    Return the value stored for the given key, or the given default value if no mapping for the key is present.
 
+.. function:: get(f::Function, collection, key)
+
+   Return the value stored for the given key, or if no mapping for the key is present, return ``f()``.  Use ``get!`` to also store the default value in the dictionary.
+
+   This is intended to be called using ``do`` block syntax::
+
+     get(dict, key) do
+         # default value calculated here
+	 time()
+     end
+
 .. function:: get!(collection, key, default)
 
    Return the value stored for the given key, or if no mapping for the key is present, store ``key => default``, and return ``default``.

test/collections.jl

@@ -150,14 +150,25 @@ d4[1001] = randstring(3)
 # get! (get with default values assigned to the given location)
 
 let
+    f(x) = x^2
     d = {8=>19}
     def = {}
     @test get!(d, 8, 5) == 19
     @test get!(d, 19, 2) == 2
-    @test get!(d, 42) do
-        int(e^2)
-    end == 7
-    @test d == {8=>19, 19=>2, 42=>7}
+
+    @test get!(d, 42) do  # d is updated with f(2)
+        f(2)
+    end == 4
+
+    @test get!(d, 42) do  # d is not updated
+        f(200)
+    end == 4
+
+    @test get(d, 13) do   # d is not updated
+        f(4)
+    end == 16
+
+    @test d == {8=>19, 19=>2, 42=>4}
 end
 
 # issue #2540