diff --git a/Project.toml b/Project.toml
index b7ff1dc7e6..ee166b39cb 100644
--- a/Project.toml
+++ b/Project.toml
@@ -15,7 +15,7 @@ Setfield = "efcf1570-3423-57d1-acb7-fd33fddbac46"
 
 [compat]
 ArgCheck = "1"
-BangBang = "0.2, 0.3"
+BangBang = "0.3.2"
 InitialValues = "0.2"
 Requires = "0.5"
 Setfield = "0.3, 0.4, 0.5"
diff --git a/benchmark/Manifest.toml b/benchmark/Manifest.toml
index 9c92e423f8..b39d0573f3 100644
--- a/benchmark/Manifest.toml
+++ b/benchmark/Manifest.toml
@@ -7,10 +7,12 @@ uuid = "dce04be8-c92d-5529-be00-80e4d2c0e197"
 version = "1.0.1"
 
 [[BangBang]]
-deps = ["Future", "InitialValues", "LinearAlgebra", "Requires", "Setfield", "ZygoteRules"]
-git-tree-sha1 = "6a721fca2a44ae40615712e6522ce1c12ac4726c"
+deps = ["Compat", "ConstructionBase", "Future", "InitialValues", "LinearAlgebra", "Requires", "Tables", "ZygoteRules"]
+git-tree-sha1 = "178ab91f57311b9375ade95bfefc8a8565263e89"
+repo-rev = "master"
+repo-url = "https://github.com/tkf/BangBang.jl.git"
 uuid = "198e06fe-97b7-11e9-32a5-e1d131e6ad66"
-version = "0.3.1"
+version = "0.3.2-DEV"
 
 [[Base64]]
 uuid = "2a0f44e3-6c83-55bd-87e4-b1978d98bd5f"
@@ -38,12 +40,22 @@ git-tree-sha1 = "e3efe0a0f49dcd294c8c73e897b4fdf891f0fbd3"
 uuid = "187b0558-2788-49d3-abe0-74a17ed4e7c9"
 version = "0.1.0"
 
+[[DataAPI]]
+git-tree-sha1 = "674b67f344687a88310213ddfa8a2b3c76cc4252"
+uuid = "9a962f9c-6df0-11e9-0e5d-c546b8b5ee8a"
+version = "1.1.0"
+
 [[DataStructures]]
 deps = ["InteractiveUtils", "OrderedCollections"]
 git-tree-sha1 = "1fe8fad5fc84686dcbc674aa255bc867a64f8132"
 uuid = "864edb3b-99cc-5e75-8d2d-829cb0a9cfe8"
 version = "0.17.5"
 
+[[DataValueInterfaces]]
+git-tree-sha1 = "bfc1187b79289637fa0ef6d4436ebdfe6905cbd6"
+uuid = "e2d170a0-9d28-54be-80f0-106bbe20a464"
+version = "1.0.0"
+
 [[Dates]]
 deps = ["Printf"]
 uuid = "ade2ca70-3891-5945-98fb-dc099432e06a"
@@ -69,6 +81,11 @@ version = "0.2.0"
 deps = ["Markdown"]
 uuid = "b77e0a4c-d291-57a0-90e8-8db25a27a240"
 
+[[IteratorInterfaceExtensions]]
+git-tree-sha1 = "a3f24677c21f5bbe9d2a714f95dcd58337fb2856"
+uuid = "82899510-4779-5014-852e-03e436cf321d"
+version = "1.0.0"
+
 [[JSON]]
 deps = ["Dates", "Mmap", "Parsers", "Unicode"]
 git-tree-sha1 = "b34d7cef7b337321e97d22242c3c2b91f476748e"
@@ -181,6 +198,18 @@ uuid = "2f01184e-e22b-5df5-ae63-d93ebab69eaf"
 deps = ["LinearAlgebra", "SparseArrays"]
 uuid = "10745b16-79ce-11e8-11f9-7d13ad32a3b2"
 
+[[TableTraits]]
+deps = ["IteratorInterfaceExtensions"]
+git-tree-sha1 = "b1ad568ba658d8cbb3b892ed5380a6f3e781a81e"
+uuid = "3783bdb8-4a98-5b6b-af9a-565f29a5fe9c"
+version = "1.0.0"
+
+[[Tables]]
+deps = ["DataAPI", "DataValueInterfaces", "IteratorInterfaceExtensions", "LinearAlgebra", "TableTraits", "Test"]
+git-tree-sha1 = "aaed7b3b00248ff6a794375ad6adf30f30ca5591"
+uuid = "bd369af6-aec1-5ad0-b16a-f7cc5008161c"
+version = "0.2.11"
+
 [[Test]]
 deps = ["Distributed", "InteractiveUtils", "Logging", "Random"]
 uuid = "8dfed614-e22c-5e08-85e1-65c5234f0b40"
@@ -194,7 +223,7 @@ version = "0.5.6"
 deps = ["ArgCheck", "BangBang", "Distributed", "InitialValues", "Logging", "Markdown", "Requires", "Setfield"]
 path = ".."
 uuid = "28d57a85-8fef-5791-bfe6-a80928e7c999"
-version = "0.4.3-DEV"
+version = "0.4.4-DEV"
 
 [[UUIDs]]
 deps = ["Random", "SHA"]
diff --git a/benchmark/Project.toml b/benchmark/Project.toml
index c0003eee34..b1efea4380 100644
--- a/benchmark/Project.toml
+++ b/benchmark/Project.toml
@@ -1,5 +1,6 @@
 [deps]
 ArgCheck = "dce04be8-c92d-5529-be00-80e4d2c0e197"
+BangBang = "198e06fe-97b7-11e9-32a5-e1d131e6ad66"
 BenchmarkTools = "6e4b80f9-dd63-53aa-95a3-0cdb28fa8baf"
 LinearAlgebra = "37e2e46d-f89d-539d-b4ee-838fcccc9c8e"
 Markdown = "d6f4376e-aef5-505a-96c1-9c027394607a"
diff --git a/docs/Manifest.toml b/docs/Manifest.toml
index d0d6a9ef54..cc78632b80 100644
--- a/docs/Manifest.toml
+++ b/docs/Manifest.toml
@@ -7,10 +7,10 @@ uuid = "dce04be8-c92d-5529-be00-80e4d2c0e197"
 version = "1.0.1"
 
 [[BangBang]]
-deps = ["ConstructionBase", "Future", "InitialValues", "LinearAlgebra", "Requires", "ZygoteRules"]
-git-tree-sha1 = "3a1f4990976144727192fad89a9e3ead0733cae5"
+deps = ["Compat", "ConstructionBase", "Future", "InitialValues", "LinearAlgebra", "Requires", "Tables", "ZygoteRules"]
+git-tree-sha1 = "178ab91f57311b9375ade95bfefc8a8565263e89"
 repo-rev = "master"
-repo-url = "https://github.com/tkf/BangBang.jl"
+repo-url = "https://github.com/tkf/BangBang.jl.git"
 uuid = "198e06fe-97b7-11e9-32a5-e1d131e6ad66"
 version = "0.3.2-DEV"
 
@@ -45,6 +45,11 @@ git-tree-sha1 = "1fe8fad5fc84686dcbc674aa255bc867a64f8132"
 uuid = "864edb3b-99cc-5e75-8d2d-829cb0a9cfe8"
 version = "0.17.5"
 
+[[DataValueInterfaces]]
+git-tree-sha1 = "bfc1187b79289637fa0ef6d4436ebdfe6905cbd6"
+uuid = "e2d170a0-9d28-54be-80f0-106bbe20a464"
+version = "1.0.0"
+
 [[Dates]]
 deps = ["Printf"]
 uuid = "ade2ca70-3891-5945-98fb-dc099432e06a"
@@ -84,6 +89,11 @@ version = "0.2.0"
 deps = ["Markdown"]
 uuid = "b77e0a4c-d291-57a0-90e8-8db25a27a240"
 
+[[IteratorInterfaceExtensions]]
+git-tree-sha1 = "a3f24677c21f5bbe9d2a714f95dcd58337fb2856"
+uuid = "82899510-4779-5014-852e-03e436cf321d"
+version = "1.0.0"
+
 [[JSON]]
 deps = ["Dates", "Mmap", "Parsers", "Unicode"]
 git-tree-sha1 = "b34d7cef7b337321e97d22242c3c2b91f476748e"
@@ -248,6 +258,18 @@ git-tree-sha1 = "20da2784e79fc0bfdd70592d1b47d7a6034e82d1"
 uuid = "7522ee7d-7047-56d0-94d9-4bc626e7058d"
 version = "0.3.0"
 
+[[TableTraits]]
+deps = ["IteratorInterfaceExtensions"]
+git-tree-sha1 = "b1ad568ba658d8cbb3b892ed5380a6f3e781a81e"
+uuid = "3783bdb8-4a98-5b6b-af9a-565f29a5fe9c"
+version = "1.0.0"
+
+[[Tables]]
+deps = ["DataAPI", "DataValueInterfaces", "IteratorInterfaceExtensions", "LinearAlgebra", "TableTraits", "Test"]
+git-tree-sha1 = "aaed7b3b00248ff6a794375ad6adf30f30ca5591"
+uuid = "bd369af6-aec1-5ad0-b16a-f7cc5008161c"
+version = "0.2.11"
+
 [[Test]]
 deps = ["Distributed", "InteractiveUtils", "Logging", "Random"]
 uuid = "8dfed614-e22c-5e08-85e1-65c5234f0b40"
@@ -261,7 +283,7 @@ version = "0.5.6"
 deps = ["ArgCheck", "BangBang", "Distributed", "InitialValues", "Logging", "Markdown", "Requires", "Setfield"]
 path = ".."
 uuid = "28d57a85-8fef-5791-bfe6-a80928e7c999"
-version = "0.4.3-DEV"
+version = "0.4.4-DEV"
 
 [[UUIDs]]
 deps = ["Random", "SHA"]
diff --git a/docs/src/manual.md b/docs/src/manual.md
index 6a992795df..f62ad26531 100644
--- a/docs/src/manual.md
+++ b/docs/src/manual.md
@@ -19,6 +19,7 @@ dtransduce
 eduction
 map!
 copy!
+copy
 append!
 Transducers.append!!
 collect
diff --git a/src/Transducers.jl b/src/Transducers.jl
index f5d24e0b6b..d5e6af172f 100644
--- a/src/Transducers.jl
+++ b/src/Transducers.jl
@@ -14,7 +14,7 @@ export Distinct
 using Base.Broadcast: Broadcasted
 
 using ArgCheck
-using BangBang: BangBang, append!!, empty!!, push!!, setindex!!
+using BangBang: BangBang, Empty, append!!, empty!!, push!!, setindex!!
 using Distributed: Distributed, @everywhere
 using Logging: LogLevel, @logmsg
 using Requires
diff --git a/src/processes.jl b/src/processes.jl
index 1a112992f6..7f57cb2c46 100644
--- a/src/processes.jl
+++ b/src/processes.jl
@@ -590,6 +590,26 @@ function Base.collect(xf::Transducer, coll)
 end
 # Base.collect(xf, coll) = append!([], xf, coll)
 
+"""
+    copy(xf::Transducer, T, foldable) :: Union{T, Nothing}
+    copy(xf::Transducer, foldable::T) :: Union{T, Nothing}
+
+Process `foldable` with a transducer `xf` and then create a container of type `T`
+filled with the result.  Return `nothing` if the transducer does not produce
+anything.  (This is because there is no consistent interface to create an empty
+container given its type and not all containers support creating an empty
+container.)
+"""
+function Base.copy(xf::Transducer, ::Type{T}, foldable) where T
+    result = append!!(Empty(T), foldable)
+    if result isa Empty
+        return nothing
+    end
+    return result
+end
+
+Base.copy(xf::Transducer, foldable::T) where T = copy(xf, T, foldable)
+
 """
     map!(xf::Transducer, dest, src; simd)
 
diff --git a/test/Manifest.toml b/test/Manifest.toml
index f3c757b20b..b1d889073e 100644
--- a/test/Manifest.toml
+++ b/test/Manifest.toml
@@ -7,10 +7,10 @@ uuid = "dce04be8-c92d-5529-be00-80e4d2c0e197"
 version = "1.0.1"
 
 [[BangBang]]
-deps = ["ConstructionBase", "Future", "InitialValues", "LinearAlgebra", "Requires", "ZygoteRules"]
-git-tree-sha1 = "3a1f4990976144727192fad89a9e3ead0733cae5"
+deps = ["Compat", "ConstructionBase", "Future", "InitialValues", "LinearAlgebra", "Requires", "Tables", "ZygoteRules"]
+git-tree-sha1 = "178ab91f57311b9375ade95bfefc8a8565263e89"
 repo-rev = "master"
-repo-url = "https://github.com/tkf/BangBang.jl"
+repo-url = "https://github.com/tkf/BangBang.jl.git"
 uuid = "198e06fe-97b7-11e9-32a5-e1d131e6ad66"
 version = "0.3.2-DEV"
 
@@ -51,6 +51,11 @@ git-tree-sha1 = "1fe8fad5fc84686dcbc674aa255bc867a64f8132"
 uuid = "864edb3b-99cc-5e75-8d2d-829cb0a9cfe8"
 version = "0.17.5"
 
+[[DataValueInterfaces]]
+git-tree-sha1 = "bfc1187b79289637fa0ef6d4436ebdfe6905cbd6"
+uuid = "e2d170a0-9d28-54be-80f0-106bbe20a464"
+version = "1.0.0"
+
 [[Dates]]
 deps = ["Printf"]
 uuid = "ade2ca70-3891-5945-98fb-dc099432e06a"
@@ -98,6 +103,11 @@ version = "0.2.0"
 deps = ["Markdown"]
 uuid = "b77e0a4c-d291-57a0-90e8-8db25a27a240"
 
+[[IteratorInterfaceExtensions]]
+git-tree-sha1 = "a3f24677c21f5bbe9d2a714f95dcd58337fb2856"
+uuid = "82899510-4779-5014-852e-03e436cf321d"
+version = "1.0.0"
+
 [[JSON]]
 deps = ["Dates", "Mmap", "Parsers", "Unicode"]
 git-tree-sha1 = "b34d7cef7b337321e97d22242c3c2b91f476748e"
@@ -268,6 +278,18 @@ git-tree-sha1 = "20da2784e79fc0bfdd70592d1b47d7a6034e82d1"
 uuid = "7522ee7d-7047-56d0-94d9-4bc626e7058d"
 version = "0.3.0"
 
+[[TableTraits]]
+deps = ["IteratorInterfaceExtensions"]
+git-tree-sha1 = "b1ad568ba658d8cbb3b892ed5380a6f3e781a81e"
+uuid = "3783bdb8-4a98-5b6b-af9a-565f29a5fe9c"
+version = "1.0.0"
+
+[[Tables]]
+deps = ["DataAPI", "DataValueInterfaces", "IteratorInterfaceExtensions", "LinearAlgebra", "TableTraits", "Test"]
+git-tree-sha1 = "aaed7b3b00248ff6a794375ad6adf30f30ca5591"
+uuid = "bd369af6-aec1-5ad0-b16a-f7cc5008161c"
+version = "0.2.11"
+
 [[Test]]
 deps = ["Distributed", "InteractiveUtils", "Logging", "Random"]
 uuid = "8dfed614-e22c-5e08-85e1-65c5234f0b40"
@@ -281,7 +303,7 @@ version = "0.5.6"
 deps = ["ArgCheck", "BangBang", "Distributed", "InitialValues", "Logging", "Markdown", "Requires", "Setfield"]
 path = ".."
 uuid = "28d57a85-8fef-5791-bfe6-a80928e7c999"
-version = "0.4.3-DEV"
+version = "0.4.4-DEV"
 
 [[UUIDs]]
 deps = ["Random", "SHA"]