From 69920dafbffcd757acff23f659263ec4b952a017 Mon Sep 17 00:00:00 2001
From: danbst <abcz2.uprola@gmail.com>
Date: Sun, 14 Jul 2019 13:17:49 +0300
Subject: [PATCH 1/7] lib: introduce `foreach` = flip map

The main purpose is to bring attention to `flip map`, which improves
code readablity. It is useful when ad-hoc anonymous function
grows two or more lines in `map` application:

```
      map (lcfg:
        let port = lcfg.port;
            portStr = if port != defaultPort then ":${toString port}" else "";
            scheme = if cfg.enableSSL then "https" else "http";
        in "${scheme}://cfg.hostName${portStr}"
      ) (getListen cfg);
```
Compare this to `foreach`-style:
```
      foreach (getListen cfg) (lcfg:
        let port = lcfg.port;
            portStr = if port != defaultPort then ":${toString port}" else "";
            scheme = if cfg.enableSSL then "https" else "http";
        in "${scheme}://cfg.hostName${portStr}"
      );
```
This is similar to Haskell's `for` (http://hackage.haskell.org/package/base-4.12.0.0/docs/Data-Traversable.html#v:for)
---
 lib/default.nix |  2 +-
 lib/lists.nix   | 13 +++++++++++++
 2 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/lib/default.nix b/lib/default.nix
index 3efaaf0f8f9e..f876c57e25c8 100644
--- a/lib/default.nix
+++ b/lib/default.nix
@@ -71,7 +71,7 @@ let
       zipAttrsWithNames zipAttrsWith zipAttrs recursiveUpdateUntil
       recursiveUpdate matchAttrs overrideExisting getOutput getBin
       getLib getDev chooseDevOutputs zipWithNames zip;
-    inherit (lists) singleton foldr fold foldl foldl' imap0 imap1
+    inherit (lists) singleton foreach foldr fold foldl foldl' imap0 imap1
       concatMap flatten remove findSingle findFirst any all count
       optional optionals toList range partition zipListsWith zipLists
       reverseList listDfs toposort sort naturalSort compareLists take
diff --git a/lib/lists.nix b/lib/lists.nix
index 30d87ece6641..f9953720ee10 100644
--- a/lib/lists.nix
+++ b/lib/lists.nix
@@ -21,6 +21,19 @@ rec {
   */
   singleton = x: [x];
 
+  /*  Apply the function to each element in the list. Same as `map`, but arguments
+      flipped.
+
+      Type: foreach :: [a] -> (a -> b) -> [b]
+
+      Example:
+        foreach [ 1 2 ] (x:
+          toString x
+        )
+        => [ "1" "2" ]
+  */
+  foreach = xs: f: map f xs;
+
   /* “right fold” a binary function `op` between successive elements of
      `list` with `nul' as the starting value, i.e.,
      `foldr op nul [x_1 x_2 ... x_n] == op x_1 (op x_2 ... (op x_n nul))`.

From 3b0534310c89d04fc3a9c5714b5a4d0f9fb0efca Mon Sep 17 00:00:00 2001
From: danbst <abcz2.uprola@gmail.com>
Date: Sun, 14 Jul 2019 13:46:10 +0300
Subject: [PATCH 2/7] mass replace "flip map -> foreach"

See `foreach`-introduction commit.
```
rg 'flip map ' --files-with-matches | xargs sed -i 's/flip map /foreach /g'
```
---
 nixos/doc/manual/default.nix                         |  2 +-
 nixos/lib/build-vms.nix                              |  6 +++---
 nixos/maintainers/option-usages.nix                  |  2 +-
 nixos/modules/rename.nix                             |  2 +-
 nixos/modules/services/monitoring/ups.nix            |  2 +-
 nixos/modules/services/networking/consul.nix         |  2 +-
 .../modules/services/networking/hylafax/systemd.nix  |  2 +-
 nixos/modules/services/networking/ssh/sshd.nix       |  2 +-
 nixos/modules/services/x11/xautolock.nix             |  2 +-
 nixos/modules/services/x11/xserver.nix               |  2 +-
 nixos/modules/system/boot/loader/grub/grub.nix       |  2 +-
 nixos/modules/tasks/network-interfaces-systemd.nix   |  8 ++++----
 nixos/modules/tasks/network-interfaces.nix           | 12 ++++++------
 nixos/tests/networking.nix                           |  2 +-
 pkgs/applications/networking/irc/weechat/wrapper.nix |  2 +-
 .../networking/remote/citrix-receiver/default.nix    |  2 +-
 .../networking/remote/citrix-workspace/default.nix   |  2 +-
 .../ibus-engines/ibus-typing-booster/wrapper.nix     |  2 +-
 18 files changed, 28 insertions(+), 28 deletions(-)

diff --git a/nixos/doc/manual/default.nix b/nixos/doc/manual/default.nix
index 7fc0ad702f84..02dfeeefe3e8 100644
--- a/nixos/doc/manual/default.nix
+++ b/nixos/doc/manual/default.nix
@@ -45,7 +45,7 @@ let
         + "</listitem>";
     in "<itemizedlist>${lib.concatStringsSep "\n" (map (p: describe (unpack p)) packages)}</itemizedlist>";
 
-  optionsListDesc = lib.flip map optionsListVisible (opt: opt // {
+  optionsListDesc = lib.foreach optionsListVisible (opt: opt // {
     # Clean up declaration sites to not refer to the NixOS source tree.
     declarations = map stripAnyPrefixes opt.declarations;
   }
diff --git a/nixos/lib/build-vms.nix b/nixos/lib/build-vms.nix
index 6c92aa1ffa2f..2ecceb82fbe0 100644
--- a/nixos/lib/build-vms.nix
+++ b/nixos/lib/build-vms.nix
@@ -54,11 +54,11 @@ rec {
 
       machinesNumbered = zipLists machines (range 1 254);
 
-      nodes_ = flip map machinesNumbered (m: nameValuePair m.fst
+      nodes_ = foreach machinesNumbered (m: nameValuePair m.fst
         [ ( { config, nodes, ... }:
             let
               interfacesNumbered = zipLists config.virtualisation.vlans (range 1 255);
-              interfaces = flip map interfacesNumbered ({ fst, snd }:
+              interfaces = foreach interfacesNumbered ({ fst, snd }:
                 nameValuePair "eth${toString snd}" { ipv4.addresses =
                   [ { address = "192.168.${toString fst}.${toString m.snd}";
                       prefixLength = 24;
@@ -88,7 +88,7 @@ rec {
                          "${config.networking.hostName}\n"));
 
                   virtualisation.qemu.options =
-                    flip map interfacesNumbered
+                    foreach interfacesNumbered
                       ({ fst, snd }: qemuNICFlags snd fst m.snd);
                 };
             }
diff --git a/nixos/maintainers/option-usages.nix b/nixos/maintainers/option-usages.nix
index a67a0ab960e5..b207eaded413 100644
--- a/nixos/maintainers/option-usages.nix
+++ b/nixos/maintainers/option-usages.nix
@@ -102,7 +102,7 @@ let
       # builtins multiply by 4 the memory usage and the time used to compute
       # each options.
       tryCollectOptions = moduleResult:
-        flip map (excludeOptions (collect isOption moduleResult)) (opt:
+        foreach (excludeOptions (collect isOption moduleResult)) (opt:
           { name = showOption opt.loc; } // builtins.tryEval (strict opt.value));
      in
        keepNames (
diff --git a/nixos/modules/rename.nix b/nixos/modules/rename.nix
index e127782e85f5..218b1d9339aa 100644
--- a/nixos/modules/rename.nix
+++ b/nixos/modules/rename.nix
@@ -248,7 +248,7 @@ with lib;
     # KSM
     (mkRenamedOptionModule [ "hardware" "enableKSM" ] [ "hardware" "ksm" "enable" ])
 
-  ] ++ (flip map [ "blackboxExporter" "collectdExporter" "fritzboxExporter"
+  ] ++ (foreach [ "blackboxExporter" "collectdExporter" "fritzboxExporter"
                    "jsonExporter" "minioExporter" "nginxExporter" "nodeExporter"
                    "snmpExporter" "unifiExporter" "varnishExporter" ]
        (opt: mkRemovedOptionModule [ "services" "prometheus" "${opt}" ] ''
diff --git a/nixos/modules/services/monitoring/ups.nix b/nixos/modules/services/monitoring/ups.nix
index bc755612fd9b..57f0bfec5745 100644
--- a/nixos/modules/services/monitoring/ups.nix
+++ b/nixos/modules/services/monitoring/ups.nix
@@ -225,7 +225,7 @@ in
         ''
           maxstartdelay = ${toString cfg.maxStartDelay}
 
-          ${flip concatStringsSep (flip map (attrValues cfg.ups) (ups: ups.summary)) "
+          ${flip concatStringsSep (foreach (attrValues cfg.ups) (ups: ups.summary)) "
 
           "}
         '';
diff --git a/nixos/modules/services/networking/consul.nix b/nixos/modules/services/networking/consul.nix
index 3a92a883fbf8..78fca9326d33 100644
--- a/nixos/modules/services/networking/consul.nix
+++ b/nixos/modules/services/networking/consul.nix
@@ -15,7 +15,7 @@ let
     ++ cfg.extraConfigFiles;
 
   devices = attrValues (filterAttrs (_: i: i != null) cfg.interface);
-  systemdDevices = flip map devices
+  systemdDevices = foreach devices
     (i: "sys-subsystem-net-devices-${utils.escapeSystemdPath i}.device");
 in
 {
diff --git a/nixos/modules/services/networking/hylafax/systemd.nix b/nixos/modules/services/networking/hylafax/systemd.nix
index ef177e4be345..527026c00762 100644
--- a/nixos/modules/services/networking/hylafax/systemd.nix
+++ b/nixos/modules/services/networking/hylafax/systemd.nix
@@ -7,7 +7,7 @@ let
   inherit (lib) concatStringsSep optionalString;
 
   cfg = config.services.hylafax;
-  mapModems = lib.flip map (lib.attrValues cfg.modems);
+  mapModems = lib.foreach (lib.attrValues cfg.modems);
 
   mkConfigFile = name: conf:
     # creates hylafax config file,
diff --git a/nixos/modules/services/networking/ssh/sshd.nix b/nixos/modules/services/networking/ssh/sshd.nix
index 0f9d2420903b..005d8bfb61fb 100644
--- a/nixos/modules/services/networking/ssh/sshd.nix
+++ b/nixos/modules/services/networking/ssh/sshd.nix
@@ -502,7 +502,7 @@ in
 
     assertions = [{ assertion = if cfg.forwardX11 then cfgc.setXAuthLocation else true;
                     message = "cannot enable X11 forwarding without setting xauth location";}]
-      ++ flip map cfg.listenAddresses ({ addr, ... }: {
+      ++ foreach cfg.listenAddresses ({ addr, ... }: {
         assertion = addr != null;
         message = "addr must be specified in each listenAddresses entry";
       });
diff --git a/nixos/modules/services/x11/xautolock.nix b/nixos/modules/services/x11/xautolock.nix
index cbe000058dc6..51bdcae992e2 100644
--- a/nixos/modules/services/x11/xautolock.nix
+++ b/nixos/modules/services/x11/xautolock.nix
@@ -129,7 +129,7 @@ in
           assertion = cfg.killer != null -> cfg.killtime >= 10;
           message = "killtime has to be at least 10 minutes according to `man xautolock`";
         }
-      ] ++ (lib.flip map [ "locker" "notifier" "nowlocker" "killer" ]
+      ] ++ (lib.foreach [ "locker" "notifier" "nowlocker" "killer" ]
         (option:
         {
           assertion = cfg."${option}" != null -> builtins.substring 0 1 cfg."${option}" == "/";
diff --git a/nixos/modules/services/x11/xserver.nix b/nixos/modules/services/x11/xserver.nix
index 82730c5e80c6..4d28a45c2ce3 100644
--- a/nixos/modules/services/x11/xserver.nix
+++ b/nixos/modules/services/x11/xserver.nix
@@ -75,7 +75,7 @@ let
   in imap1 mkHead cfg.xrandrHeads;
 
   xrandrDeviceSection = let
-    monitors = flip map xrandrHeads (h: ''
+    monitors = foreach xrandrHeads (h: ''
       Option "monitor-${h.config.output}" "${h.name}"
     '');
     # First option is indented through the space in the config but any
diff --git a/nixos/modules/system/boot/loader/grub/grub.nix b/nixos/modules/system/boot/loader/grub/grub.nix
index 4e4d14985b0d..84753d77cc4c 100644
--- a/nixos/modules/system/boot/loader/grub/grub.nix
+++ b/nixos/modules/system/boot/loader/grub/grub.nix
@@ -684,7 +684,7 @@ in
           assertion = if args.efiSysMountPoint == null then true else hasPrefix "/" args.efiSysMountPoint;
           message = "EFI paths must be absolute, not ${args.efiSysMountPoint}";
         }
-      ] ++ flip map args.devices (device: {
+      ] ++ foreach args.devices (device: {
         assertion = device == "nodev" || hasPrefix "/" device;
         message = "GRUB devices must be absolute paths, not ${device} in ${args.path}";
       }));
diff --git a/nixos/modules/tasks/network-interfaces-systemd.nix b/nixos/modules/tasks/network-interfaces-systemd.nix
index 857aaf1e6e30..2612d13da4f8 100644
--- a/nixos/modules/tasks/network-interfaces-systemd.nix
+++ b/nixos/modules/tasks/network-interfaces-systemd.nix
@@ -74,7 +74,7 @@ in
         enable = true;
         networks."99-main" = genericNetwork mkDefault;
       }
-      (mkMerge (flip map interfaces (i: {
+      (mkMerge (foreach interfaces (i: {
         netdevs = mkIf i.virtual ({
           "40-${i.name}" = {
             netdevConfig = {
@@ -90,7 +90,7 @@ in
           name = mkDefault i.name;
           DHCP = mkForce (dhcpStr
             (if i.useDHCP != null then i.useDHCP else cfg.useDHCP && interfaceIps i == [ ]));
-          address = flip map (interfaceIps i)
+          address = foreach (interfaceIps i)
             (ip: "${ip.address}/${toString ip.prefixLength}");
           networkConfig.IPv6PrivacyExtensions = "kernel";
         } ];
@@ -102,7 +102,7 @@ in
             Kind = "bridge";
           };
         };
-        networks = listToAttrs (flip map bridge.interfaces (bi:
+        networks = listToAttrs (foreach bridge.interfaces (bi:
           nameValuePair "40-${bi}" (mkMerge [ (genericNetwork (mkOverride 999)) {
             DHCP = mkOverride 0 (dhcpStr false);
             networkConfig.Bridge = name;
@@ -173,7 +173,7 @@ in
 
         };
 
-        networks = listToAttrs (flip map bond.interfaces (bi:
+        networks = listToAttrs (foreach bond.interfaces (bi:
           nameValuePair "40-${bi}" (mkMerge [ (genericNetwork (mkOverride 999)) {
             DHCP = mkOverride 0 (dhcpStr false);
             networkConfig.Bond = name;
diff --git a/nixos/modules/tasks/network-interfaces.nix b/nixos/modules/tasks/network-interfaces.nix
index f9b0eb330bf8..2af20e05b051 100644
--- a/nixos/modules/tasks/network-interfaces.nix
+++ b/nixos/modules/tasks/network-interfaces.nix
@@ -926,7 +926,7 @@ in
     warnings = concatMap (i: i.warnings) interfaces;
 
     assertions =
-      (flip map interfaces (i: {
+      (foreach interfaces (i: {
         # With the linux kernel, interface name length is limited by IFNAMSIZ
         # to 16 bytes, including the trailing null byte.
         # See include/linux/if.h in the kernel sources
@@ -934,12 +934,12 @@ in
         message = ''
           The name of networking.interfaces."${i.name}" is too long, it needs to be less than 16 characters.
         '';
-      })) ++ (flip map slaveIfs (i: {
+      })) ++ (foreach slaveIfs (i: {
         assertion = i.ipv4.addresses == [ ] && i.ipv6.addresses == [ ];
         message = ''
           The networking.interfaces."${i.name}" must not have any defined ips when it is a slave.
         '';
-      })) ++ (flip map interfaces (i: {
+      })) ++ (foreach interfaces (i: {
         assertion = i.preferTempAddress -> cfg.enableIPv6;
         message = ''
           Temporary addresses are only needed when IPv6 is enabled.
@@ -967,8 +967,8 @@ in
       "net.ipv6.conf.default.disable_ipv6" = mkDefault (!cfg.enableIPv6);
       "net.ipv6.conf.all.forwarding" = mkDefault (any (i: i.proxyARP) interfaces);
     } // listToAttrs (flip concatMap (filter (i: i.proxyARP) interfaces)
-        (i: flip map [ "4" "6" ] (v: nameValuePair "net.ipv${v}.conf.${i.name}.proxy_arp" true)))
-      // listToAttrs (flip map (filter (i: i.preferTempAddress) interfaces)
+        (i: foreach [ "4" "6" ] (v: nameValuePair "net.ipv${v}.conf.${i.name}.proxy_arp" true)))
+      // listToAttrs (foreach (filter (i: i.preferTempAddress) interfaces)
         (i: nameValuePair "net.ipv6.conf.${i.name}.use_tempaddr" 2));
 
     # Capabilities won't work unless we have at-least a 4.3 Linux
@@ -1051,7 +1051,7 @@ in
           ${cfg.localCommands}
         '';
       };
-    } // (listToAttrs (flip map interfaces (i:
+    } // (listToAttrs (foreach interfaces (i:
       let
         deviceDependency = if (config.boot.isContainer || i.name == "lo")
           then []
diff --git a/nixos/tests/networking.nix b/nixos/tests/networking.nix
index ed9f287d5582..9553b52850e9 100644
--- a/nixos/tests/networking.nix
+++ b/nixos/tests/networking.nix
@@ -21,7 +21,7 @@ let
         useNetworkd = networkd;
         firewall.checkReversePath = true;
         firewall.allowedUDPPorts = [ 547 ];
-        interfaces = mkOverride 0 (listToAttrs (flip map vlanIfs (n:
+        interfaces = mkOverride 0 (listToAttrs (foreach vlanIfs (n:
           nameValuePair "eth${toString n}" {
             ipv4.addresses = [ { address = "192.168.${toString n}.1"; prefixLength = 24; } ];
             ipv6.addresses = [ { address = "fd00:1234:5678:${toString n}::1"; prefixLength = 64; } ];
diff --git a/pkgs/applications/networking/irc/weechat/wrapper.nix b/pkgs/applications/networking/irc/weechat/wrapper.nix
index 6dcd9a31e5e0..502a7917a094 100644
--- a/pkgs/applications/networking/irc/weechat/wrapper.nix
+++ b/pkgs/applications/networking/irc/weechat/wrapper.nix
@@ -54,7 +54,7 @@ let
     init = let
       init = builtins.replaceStrings [ "\n" ] [ ";" ] (config.init or "");
 
-      mkScript = drv: lib.flip map drv.scripts (script: "/script load ${drv}/share/${script}");
+      mkScript = drv: lib.foreach drv.scripts (script: "/script load ${drv}/share/${script}");
 
       scripts = builtins.concatStringsSep ";" (lib.foldl (scripts: drv: scripts ++ mkScript drv)
         [ ] (config.scripts or []));
diff --git a/pkgs/applications/networking/remote/citrix-receiver/default.nix b/pkgs/applications/networking/remote/citrix-receiver/default.nix
index d6e25ae4e7b5..7bf465ef94a6 100644
--- a/pkgs/applications/networking/remote/citrix-receiver/default.nix
+++ b/pkgs/applications/networking/remote/citrix-receiver/default.nix
@@ -58,7 +58,7 @@ let
       versions = [ "13.8.0" "13.9.0" "13.9.1" ];
     in
       lib.listToAttrs
-        (lib.flip map versions
+        (lib.foreach versions
           (v: lib.nameValuePair v (throw "Unsupported citrix_receiver version: ${v}")));
   in
     deprecatedVersions // supportedVersions;
diff --git a/pkgs/applications/networking/remote/citrix-workspace/default.nix b/pkgs/applications/networking/remote/citrix-workspace/default.nix
index 13a16a6e2245..665a8669fe29 100644
--- a/pkgs/applications/networking/remote/citrix-workspace/default.nix
+++ b/pkgs/applications/networking/remote/citrix-workspace/default.nix
@@ -59,7 +59,7 @@ let
       versions = [ ];
     in
       lib.listToAttrs
-        (lib.flip map versions
+        (lib.foreach versions
           (v: lib.nameValuePair v (throw "Unsupported citrix_workspace version: ${v}")));
   in
     deprecatedVersions // supportedVersions;
diff --git a/pkgs/tools/inputmethods/ibus-engines/ibus-typing-booster/wrapper.nix b/pkgs/tools/inputmethods/ibus-engines/ibus-typing-booster/wrapper.nix
index 1115e4e232fc..9fcaea2925c1 100644
--- a/pkgs/tools/inputmethods/ibus-engines/ibus-typing-booster/wrapper.nix
+++ b/pkgs/tools/inputmethods/ibus-engines/ibus-typing-booster/wrapper.nix
@@ -4,7 +4,7 @@
 
 let
 
-  hunspellDirs = with lib; makeSearchPath ":" (flatten (flip map langs (lang: [
+  hunspellDirs = with lib; makeSearchPath ":" (flatten (foreach langs (lang: [
     "${hunspellDicts.${lang}}/share/hunspell"
     "${hunspellDicts.${lang}}/share/myspell"
     "${hunspellDicts.${lang}}/share/myspell/dicts"

From 91bb646e98808d594b339d3386f7963a546ccfb4 Mon Sep 17 00:00:00 2001
From: danbst <abcz2.uprola@gmail.com>
Date: Mon, 5 Aug 2019 14:01:45 +0300
Subject: [PATCH 3/7] Revert "mass replace "flip map -> foreach""

This reverts commit 3b0534310c89d04fc3a9c5714b5a4d0f9fb0efca.
---
 nixos/doc/manual/default.nix                         |  2 +-
 nixos/lib/build-vms.nix                              |  6 +++---
 nixos/maintainers/option-usages.nix                  |  2 +-
 nixos/modules/rename.nix                             |  2 +-
 nixos/modules/services/monitoring/ups.nix            |  2 +-
 nixos/modules/services/networking/consul.nix         |  2 +-
 .../modules/services/networking/hylafax/systemd.nix  |  2 +-
 nixos/modules/services/networking/ssh/sshd.nix       |  2 +-
 nixos/modules/services/x11/xautolock.nix             |  2 +-
 nixos/modules/services/x11/xserver.nix               |  2 +-
 nixos/modules/system/boot/loader/grub/grub.nix       |  2 +-
 nixos/modules/tasks/network-interfaces-systemd.nix   |  8 ++++----
 nixos/modules/tasks/network-interfaces.nix           | 12 ++++++------
 nixos/tests/networking.nix                           |  2 +-
 pkgs/applications/networking/irc/weechat/wrapper.nix |  2 +-
 .../networking/remote/citrix-receiver/default.nix    |  2 +-
 .../networking/remote/citrix-workspace/default.nix   |  2 +-
 .../ibus-engines/ibus-typing-booster/wrapper.nix     |  2 +-
 18 files changed, 28 insertions(+), 28 deletions(-)

diff --git a/nixos/doc/manual/default.nix b/nixos/doc/manual/default.nix
index 02dfeeefe3e8..7fc0ad702f84 100644
--- a/nixos/doc/manual/default.nix
+++ b/nixos/doc/manual/default.nix
@@ -45,7 +45,7 @@ let
         + "</listitem>";
     in "<itemizedlist>${lib.concatStringsSep "\n" (map (p: describe (unpack p)) packages)}</itemizedlist>";
 
-  optionsListDesc = lib.foreach optionsListVisible (opt: opt // {
+  optionsListDesc = lib.flip map optionsListVisible (opt: opt // {
     # Clean up declaration sites to not refer to the NixOS source tree.
     declarations = map stripAnyPrefixes opt.declarations;
   }
diff --git a/nixos/lib/build-vms.nix b/nixos/lib/build-vms.nix
index 2ecceb82fbe0..6c92aa1ffa2f 100644
--- a/nixos/lib/build-vms.nix
+++ b/nixos/lib/build-vms.nix
@@ -54,11 +54,11 @@ rec {
 
       machinesNumbered = zipLists machines (range 1 254);
 
-      nodes_ = foreach machinesNumbered (m: nameValuePair m.fst
+      nodes_ = flip map machinesNumbered (m: nameValuePair m.fst
         [ ( { config, nodes, ... }:
             let
               interfacesNumbered = zipLists config.virtualisation.vlans (range 1 255);
-              interfaces = foreach interfacesNumbered ({ fst, snd }:
+              interfaces = flip map interfacesNumbered ({ fst, snd }:
                 nameValuePair "eth${toString snd}" { ipv4.addresses =
                   [ { address = "192.168.${toString fst}.${toString m.snd}";
                       prefixLength = 24;
@@ -88,7 +88,7 @@ rec {
                          "${config.networking.hostName}\n"));
 
                   virtualisation.qemu.options =
-                    foreach interfacesNumbered
+                    flip map interfacesNumbered
                       ({ fst, snd }: qemuNICFlags snd fst m.snd);
                 };
             }
diff --git a/nixos/maintainers/option-usages.nix b/nixos/maintainers/option-usages.nix
index b207eaded413..a67a0ab960e5 100644
--- a/nixos/maintainers/option-usages.nix
+++ b/nixos/maintainers/option-usages.nix
@@ -102,7 +102,7 @@ let
       # builtins multiply by 4 the memory usage and the time used to compute
       # each options.
       tryCollectOptions = moduleResult:
-        foreach (excludeOptions (collect isOption moduleResult)) (opt:
+        flip map (excludeOptions (collect isOption moduleResult)) (opt:
           { name = showOption opt.loc; } // builtins.tryEval (strict opt.value));
      in
        keepNames (
diff --git a/nixos/modules/rename.nix b/nixos/modules/rename.nix
index 218b1d9339aa..e127782e85f5 100644
--- a/nixos/modules/rename.nix
+++ b/nixos/modules/rename.nix
@@ -248,7 +248,7 @@ with lib;
     # KSM
     (mkRenamedOptionModule [ "hardware" "enableKSM" ] [ "hardware" "ksm" "enable" ])
 
-  ] ++ (foreach [ "blackboxExporter" "collectdExporter" "fritzboxExporter"
+  ] ++ (flip map [ "blackboxExporter" "collectdExporter" "fritzboxExporter"
                    "jsonExporter" "minioExporter" "nginxExporter" "nodeExporter"
                    "snmpExporter" "unifiExporter" "varnishExporter" ]
        (opt: mkRemovedOptionModule [ "services" "prometheus" "${opt}" ] ''
diff --git a/nixos/modules/services/monitoring/ups.nix b/nixos/modules/services/monitoring/ups.nix
index 57f0bfec5745..bc755612fd9b 100644
--- a/nixos/modules/services/monitoring/ups.nix
+++ b/nixos/modules/services/monitoring/ups.nix
@@ -225,7 +225,7 @@ in
         ''
           maxstartdelay = ${toString cfg.maxStartDelay}
 
-          ${flip concatStringsSep (foreach (attrValues cfg.ups) (ups: ups.summary)) "
+          ${flip concatStringsSep (flip map (attrValues cfg.ups) (ups: ups.summary)) "
 
           "}
         '';
diff --git a/nixos/modules/services/networking/consul.nix b/nixos/modules/services/networking/consul.nix
index 78fca9326d33..3a92a883fbf8 100644
--- a/nixos/modules/services/networking/consul.nix
+++ b/nixos/modules/services/networking/consul.nix
@@ -15,7 +15,7 @@ let
     ++ cfg.extraConfigFiles;
 
   devices = attrValues (filterAttrs (_: i: i != null) cfg.interface);
-  systemdDevices = foreach devices
+  systemdDevices = flip map devices
     (i: "sys-subsystem-net-devices-${utils.escapeSystemdPath i}.device");
 in
 {
diff --git a/nixos/modules/services/networking/hylafax/systemd.nix b/nixos/modules/services/networking/hylafax/systemd.nix
index 527026c00762..ef177e4be345 100644
--- a/nixos/modules/services/networking/hylafax/systemd.nix
+++ b/nixos/modules/services/networking/hylafax/systemd.nix
@@ -7,7 +7,7 @@ let
   inherit (lib) concatStringsSep optionalString;
 
   cfg = config.services.hylafax;
-  mapModems = lib.foreach (lib.attrValues cfg.modems);
+  mapModems = lib.flip map (lib.attrValues cfg.modems);
 
   mkConfigFile = name: conf:
     # creates hylafax config file,
diff --git a/nixos/modules/services/networking/ssh/sshd.nix b/nixos/modules/services/networking/ssh/sshd.nix
index 005d8bfb61fb..0f9d2420903b 100644
--- a/nixos/modules/services/networking/ssh/sshd.nix
+++ b/nixos/modules/services/networking/ssh/sshd.nix
@@ -502,7 +502,7 @@ in
 
     assertions = [{ assertion = if cfg.forwardX11 then cfgc.setXAuthLocation else true;
                     message = "cannot enable X11 forwarding without setting xauth location";}]
-      ++ foreach cfg.listenAddresses ({ addr, ... }: {
+      ++ flip map cfg.listenAddresses ({ addr, ... }: {
         assertion = addr != null;
         message = "addr must be specified in each listenAddresses entry";
       });
diff --git a/nixos/modules/services/x11/xautolock.nix b/nixos/modules/services/x11/xautolock.nix
index 51bdcae992e2..cbe000058dc6 100644
--- a/nixos/modules/services/x11/xautolock.nix
+++ b/nixos/modules/services/x11/xautolock.nix
@@ -129,7 +129,7 @@ in
           assertion = cfg.killer != null -> cfg.killtime >= 10;
           message = "killtime has to be at least 10 minutes according to `man xautolock`";
         }
-      ] ++ (lib.foreach [ "locker" "notifier" "nowlocker" "killer" ]
+      ] ++ (lib.flip map [ "locker" "notifier" "nowlocker" "killer" ]
         (option:
         {
           assertion = cfg."${option}" != null -> builtins.substring 0 1 cfg."${option}" == "/";
diff --git a/nixos/modules/services/x11/xserver.nix b/nixos/modules/services/x11/xserver.nix
index 4d28a45c2ce3..82730c5e80c6 100644
--- a/nixos/modules/services/x11/xserver.nix
+++ b/nixos/modules/services/x11/xserver.nix
@@ -75,7 +75,7 @@ let
   in imap1 mkHead cfg.xrandrHeads;
 
   xrandrDeviceSection = let
-    monitors = foreach xrandrHeads (h: ''
+    monitors = flip map xrandrHeads (h: ''
       Option "monitor-${h.config.output}" "${h.name}"
     '');
     # First option is indented through the space in the config but any
diff --git a/nixos/modules/system/boot/loader/grub/grub.nix b/nixos/modules/system/boot/loader/grub/grub.nix
index 84753d77cc4c..4e4d14985b0d 100644
--- a/nixos/modules/system/boot/loader/grub/grub.nix
+++ b/nixos/modules/system/boot/loader/grub/grub.nix
@@ -684,7 +684,7 @@ in
           assertion = if args.efiSysMountPoint == null then true else hasPrefix "/" args.efiSysMountPoint;
           message = "EFI paths must be absolute, not ${args.efiSysMountPoint}";
         }
-      ] ++ foreach args.devices (device: {
+      ] ++ flip map args.devices (device: {
         assertion = device == "nodev" || hasPrefix "/" device;
         message = "GRUB devices must be absolute paths, not ${device} in ${args.path}";
       }));
diff --git a/nixos/modules/tasks/network-interfaces-systemd.nix b/nixos/modules/tasks/network-interfaces-systemd.nix
index 2612d13da4f8..857aaf1e6e30 100644
--- a/nixos/modules/tasks/network-interfaces-systemd.nix
+++ b/nixos/modules/tasks/network-interfaces-systemd.nix
@@ -74,7 +74,7 @@ in
         enable = true;
         networks."99-main" = genericNetwork mkDefault;
       }
-      (mkMerge (foreach interfaces (i: {
+      (mkMerge (flip map interfaces (i: {
         netdevs = mkIf i.virtual ({
           "40-${i.name}" = {
             netdevConfig = {
@@ -90,7 +90,7 @@ in
           name = mkDefault i.name;
           DHCP = mkForce (dhcpStr
             (if i.useDHCP != null then i.useDHCP else cfg.useDHCP && interfaceIps i == [ ]));
-          address = foreach (interfaceIps i)
+          address = flip map (interfaceIps i)
             (ip: "${ip.address}/${toString ip.prefixLength}");
           networkConfig.IPv6PrivacyExtensions = "kernel";
         } ];
@@ -102,7 +102,7 @@ in
             Kind = "bridge";
           };
         };
-        networks = listToAttrs (foreach bridge.interfaces (bi:
+        networks = listToAttrs (flip map bridge.interfaces (bi:
           nameValuePair "40-${bi}" (mkMerge [ (genericNetwork (mkOverride 999)) {
             DHCP = mkOverride 0 (dhcpStr false);
             networkConfig.Bridge = name;
@@ -173,7 +173,7 @@ in
 
         };
 
-        networks = listToAttrs (foreach bond.interfaces (bi:
+        networks = listToAttrs (flip map bond.interfaces (bi:
           nameValuePair "40-${bi}" (mkMerge [ (genericNetwork (mkOverride 999)) {
             DHCP = mkOverride 0 (dhcpStr false);
             networkConfig.Bond = name;
diff --git a/nixos/modules/tasks/network-interfaces.nix b/nixos/modules/tasks/network-interfaces.nix
index 2af20e05b051..f9b0eb330bf8 100644
--- a/nixos/modules/tasks/network-interfaces.nix
+++ b/nixos/modules/tasks/network-interfaces.nix
@@ -926,7 +926,7 @@ in
     warnings = concatMap (i: i.warnings) interfaces;
 
     assertions =
-      (foreach interfaces (i: {
+      (flip map interfaces (i: {
         # With the linux kernel, interface name length is limited by IFNAMSIZ
         # to 16 bytes, including the trailing null byte.
         # See include/linux/if.h in the kernel sources
@@ -934,12 +934,12 @@ in
         message = ''
           The name of networking.interfaces."${i.name}" is too long, it needs to be less than 16 characters.
         '';
-      })) ++ (foreach slaveIfs (i: {
+      })) ++ (flip map slaveIfs (i: {
         assertion = i.ipv4.addresses == [ ] && i.ipv6.addresses == [ ];
         message = ''
           The networking.interfaces."${i.name}" must not have any defined ips when it is a slave.
         '';
-      })) ++ (foreach interfaces (i: {
+      })) ++ (flip map interfaces (i: {
         assertion = i.preferTempAddress -> cfg.enableIPv6;
         message = ''
           Temporary addresses are only needed when IPv6 is enabled.
@@ -967,8 +967,8 @@ in
       "net.ipv6.conf.default.disable_ipv6" = mkDefault (!cfg.enableIPv6);
       "net.ipv6.conf.all.forwarding" = mkDefault (any (i: i.proxyARP) interfaces);
     } // listToAttrs (flip concatMap (filter (i: i.proxyARP) interfaces)
-        (i: foreach [ "4" "6" ] (v: nameValuePair "net.ipv${v}.conf.${i.name}.proxy_arp" true)))
-      // listToAttrs (foreach (filter (i: i.preferTempAddress) interfaces)
+        (i: flip map [ "4" "6" ] (v: nameValuePair "net.ipv${v}.conf.${i.name}.proxy_arp" true)))
+      // listToAttrs (flip map (filter (i: i.preferTempAddress) interfaces)
         (i: nameValuePair "net.ipv6.conf.${i.name}.use_tempaddr" 2));
 
     # Capabilities won't work unless we have at-least a 4.3 Linux
@@ -1051,7 +1051,7 @@ in
           ${cfg.localCommands}
         '';
       };
-    } // (listToAttrs (foreach interfaces (i:
+    } // (listToAttrs (flip map interfaces (i:
       let
         deviceDependency = if (config.boot.isContainer || i.name == "lo")
           then []
diff --git a/nixos/tests/networking.nix b/nixos/tests/networking.nix
index 9553b52850e9..ed9f287d5582 100644
--- a/nixos/tests/networking.nix
+++ b/nixos/tests/networking.nix
@@ -21,7 +21,7 @@ let
         useNetworkd = networkd;
         firewall.checkReversePath = true;
         firewall.allowedUDPPorts = [ 547 ];
-        interfaces = mkOverride 0 (listToAttrs (foreach vlanIfs (n:
+        interfaces = mkOverride 0 (listToAttrs (flip map vlanIfs (n:
           nameValuePair "eth${toString n}" {
             ipv4.addresses = [ { address = "192.168.${toString n}.1"; prefixLength = 24; } ];
             ipv6.addresses = [ { address = "fd00:1234:5678:${toString n}::1"; prefixLength = 64; } ];
diff --git a/pkgs/applications/networking/irc/weechat/wrapper.nix b/pkgs/applications/networking/irc/weechat/wrapper.nix
index 502a7917a094..6dcd9a31e5e0 100644
--- a/pkgs/applications/networking/irc/weechat/wrapper.nix
+++ b/pkgs/applications/networking/irc/weechat/wrapper.nix
@@ -54,7 +54,7 @@ let
     init = let
       init = builtins.replaceStrings [ "\n" ] [ ";" ] (config.init or "");
 
-      mkScript = drv: lib.foreach drv.scripts (script: "/script load ${drv}/share/${script}");
+      mkScript = drv: lib.flip map drv.scripts (script: "/script load ${drv}/share/${script}");
 
       scripts = builtins.concatStringsSep ";" (lib.foldl (scripts: drv: scripts ++ mkScript drv)
         [ ] (config.scripts or []));
diff --git a/pkgs/applications/networking/remote/citrix-receiver/default.nix b/pkgs/applications/networking/remote/citrix-receiver/default.nix
index 7bf465ef94a6..d6e25ae4e7b5 100644
--- a/pkgs/applications/networking/remote/citrix-receiver/default.nix
+++ b/pkgs/applications/networking/remote/citrix-receiver/default.nix
@@ -58,7 +58,7 @@ let
       versions = [ "13.8.0" "13.9.0" "13.9.1" ];
     in
       lib.listToAttrs
-        (lib.foreach versions
+        (lib.flip map versions
           (v: lib.nameValuePair v (throw "Unsupported citrix_receiver version: ${v}")));
   in
     deprecatedVersions // supportedVersions;
diff --git a/pkgs/applications/networking/remote/citrix-workspace/default.nix b/pkgs/applications/networking/remote/citrix-workspace/default.nix
index 665a8669fe29..13a16a6e2245 100644
--- a/pkgs/applications/networking/remote/citrix-workspace/default.nix
+++ b/pkgs/applications/networking/remote/citrix-workspace/default.nix
@@ -59,7 +59,7 @@ let
       versions = [ ];
     in
       lib.listToAttrs
-        (lib.foreach versions
+        (lib.flip map versions
           (v: lib.nameValuePair v (throw "Unsupported citrix_workspace version: ${v}")));
   in
     deprecatedVersions // supportedVersions;
diff --git a/pkgs/tools/inputmethods/ibus-engines/ibus-typing-booster/wrapper.nix b/pkgs/tools/inputmethods/ibus-engines/ibus-typing-booster/wrapper.nix
index 9fcaea2925c1..1115e4e232fc 100644
--- a/pkgs/tools/inputmethods/ibus-engines/ibus-typing-booster/wrapper.nix
+++ b/pkgs/tools/inputmethods/ibus-engines/ibus-typing-booster/wrapper.nix
@@ -4,7 +4,7 @@
 
 let
 
-  hunspellDirs = with lib; makeSearchPath ":" (flatten (foreach langs (lang: [
+  hunspellDirs = with lib; makeSearchPath ":" (flatten (flip map langs (lang: [
     "${hunspellDicts.${lang}}/share/hunspell"
     "${hunspellDicts.${lang}}/share/myspell"
     "${hunspellDicts.${lang}}/share/myspell/dicts"

From 0f8596ab3f05321e36d9bd53ea7f048b7f0b62e3 Mon Sep 17 00:00:00 2001
From: danbst <abcz2.uprola@gmail.com>
Date: Mon, 5 Aug 2019 14:03:38 +0300
Subject: [PATCH 4/7] mass replace "flip map -> forEach"

See `forEach`-introduction commit.
```
rg 'flip map ' --files-with-matches | xargs sed -i 's/flip map /forEach /g'
```
---
 nixos/doc/manual/default.nix                         |  2 +-
 nixos/lib/build-vms.nix                              |  6 +++---
 nixos/maintainers/option-usages.nix                  |  2 +-
 nixos/modules/rename.nix                             |  2 +-
 nixos/modules/services/monitoring/ups.nix            |  2 +-
 nixos/modules/services/networking/consul.nix         |  2 +-
 .../modules/services/networking/hylafax/systemd.nix  |  2 +-
 nixos/modules/services/networking/ssh/sshd.nix       |  2 +-
 nixos/modules/services/x11/xautolock.nix             |  2 +-
 nixos/modules/services/x11/xserver.nix               |  2 +-
 nixos/modules/system/boot/loader/grub/grub.nix       |  2 +-
 nixos/modules/tasks/network-interfaces-systemd.nix   |  8 ++++----
 nixos/modules/tasks/network-interfaces.nix           | 12 ++++++------
 nixos/tests/networking.nix                           |  2 +-
 pkgs/applications/networking/irc/weechat/wrapper.nix |  2 +-
 .../networking/remote/citrix-receiver/default.nix    |  2 +-
 .../networking/remote/citrix-workspace/default.nix   |  2 +-
 .../ibus-engines/ibus-typing-booster/wrapper.nix     |  2 +-
 18 files changed, 28 insertions(+), 28 deletions(-)

diff --git a/nixos/doc/manual/default.nix b/nixos/doc/manual/default.nix
index 7fc0ad702f84..0963560a5bfb 100644
--- a/nixos/doc/manual/default.nix
+++ b/nixos/doc/manual/default.nix
@@ -45,7 +45,7 @@ let
         + "</listitem>";
     in "<itemizedlist>${lib.concatStringsSep "\n" (map (p: describe (unpack p)) packages)}</itemizedlist>";
 
-  optionsListDesc = lib.flip map optionsListVisible (opt: opt // {
+  optionsListDesc = lib.forEach optionsListVisible (opt: opt // {
     # Clean up declaration sites to not refer to the NixOS source tree.
     declarations = map stripAnyPrefixes opt.declarations;
   }
diff --git a/nixos/lib/build-vms.nix b/nixos/lib/build-vms.nix
index 6c92aa1ffa2f..00ab189be0ff 100644
--- a/nixos/lib/build-vms.nix
+++ b/nixos/lib/build-vms.nix
@@ -54,11 +54,11 @@ rec {
 
       machinesNumbered = zipLists machines (range 1 254);
 
-      nodes_ = flip map machinesNumbered (m: nameValuePair m.fst
+      nodes_ = forEach machinesNumbered (m: nameValuePair m.fst
         [ ( { config, nodes, ... }:
             let
               interfacesNumbered = zipLists config.virtualisation.vlans (range 1 255);
-              interfaces = flip map interfacesNumbered ({ fst, snd }:
+              interfaces = forEach interfacesNumbered ({ fst, snd }:
                 nameValuePair "eth${toString snd}" { ipv4.addresses =
                   [ { address = "192.168.${toString fst}.${toString m.snd}";
                       prefixLength = 24;
@@ -88,7 +88,7 @@ rec {
                          "${config.networking.hostName}\n"));
 
                   virtualisation.qemu.options =
-                    flip map interfacesNumbered
+                    forEach interfacesNumbered
                       ({ fst, snd }: qemuNICFlags snd fst m.snd);
                 };
             }
diff --git a/nixos/maintainers/option-usages.nix b/nixos/maintainers/option-usages.nix
index a67a0ab960e5..11247666ecda 100644
--- a/nixos/maintainers/option-usages.nix
+++ b/nixos/maintainers/option-usages.nix
@@ -102,7 +102,7 @@ let
       # builtins multiply by 4 the memory usage and the time used to compute
       # each options.
       tryCollectOptions = moduleResult:
-        flip map (excludeOptions (collect isOption moduleResult)) (opt:
+        forEach (excludeOptions (collect isOption moduleResult)) (opt:
           { name = showOption opt.loc; } // builtins.tryEval (strict opt.value));
      in
        keepNames (
diff --git a/nixos/modules/rename.nix b/nixos/modules/rename.nix
index e127782e85f5..c226f28034d5 100644
--- a/nixos/modules/rename.nix
+++ b/nixos/modules/rename.nix
@@ -248,7 +248,7 @@ with lib;
     # KSM
     (mkRenamedOptionModule [ "hardware" "enableKSM" ] [ "hardware" "ksm" "enable" ])
 
-  ] ++ (flip map [ "blackboxExporter" "collectdExporter" "fritzboxExporter"
+  ] ++ (forEach [ "blackboxExporter" "collectdExporter" "fritzboxExporter"
                    "jsonExporter" "minioExporter" "nginxExporter" "nodeExporter"
                    "snmpExporter" "unifiExporter" "varnishExporter" ]
        (opt: mkRemovedOptionModule [ "services" "prometheus" "${opt}" ] ''
diff --git a/nixos/modules/services/monitoring/ups.nix b/nixos/modules/services/monitoring/ups.nix
index bc755612fd9b..429b40227d47 100644
--- a/nixos/modules/services/monitoring/ups.nix
+++ b/nixos/modules/services/monitoring/ups.nix
@@ -225,7 +225,7 @@ in
         ''
           maxstartdelay = ${toString cfg.maxStartDelay}
 
-          ${flip concatStringsSep (flip map (attrValues cfg.ups) (ups: ups.summary)) "
+          ${flip concatStringsSep (forEach (attrValues cfg.ups) (ups: ups.summary)) "
 
           "}
         '';
diff --git a/nixos/modules/services/networking/consul.nix b/nixos/modules/services/networking/consul.nix
index 3a92a883fbf8..f080f12eaccd 100644
--- a/nixos/modules/services/networking/consul.nix
+++ b/nixos/modules/services/networking/consul.nix
@@ -15,7 +15,7 @@ let
     ++ cfg.extraConfigFiles;
 
   devices = attrValues (filterAttrs (_: i: i != null) cfg.interface);
-  systemdDevices = flip map devices
+  systemdDevices = forEach devices
     (i: "sys-subsystem-net-devices-${utils.escapeSystemdPath i}.device");
 in
 {
diff --git a/nixos/modules/services/networking/hylafax/systemd.nix b/nixos/modules/services/networking/hylafax/systemd.nix
index ef177e4be345..0c6602e7f8ab 100644
--- a/nixos/modules/services/networking/hylafax/systemd.nix
+++ b/nixos/modules/services/networking/hylafax/systemd.nix
@@ -7,7 +7,7 @@ let
   inherit (lib) concatStringsSep optionalString;
 
   cfg = config.services.hylafax;
-  mapModems = lib.flip map (lib.attrValues cfg.modems);
+  mapModems = lib.forEach (lib.attrValues cfg.modems);
 
   mkConfigFile = name: conf:
     # creates hylafax config file,
diff --git a/nixos/modules/services/networking/ssh/sshd.nix b/nixos/modules/services/networking/ssh/sshd.nix
index 0f9d2420903b..91fc7d72bc6d 100644
--- a/nixos/modules/services/networking/ssh/sshd.nix
+++ b/nixos/modules/services/networking/ssh/sshd.nix
@@ -502,7 +502,7 @@ in
 
     assertions = [{ assertion = if cfg.forwardX11 then cfgc.setXAuthLocation else true;
                     message = "cannot enable X11 forwarding without setting xauth location";}]
-      ++ flip map cfg.listenAddresses ({ addr, ... }: {
+      ++ forEach cfg.listenAddresses ({ addr, ... }: {
         assertion = addr != null;
         message = "addr must be specified in each listenAddresses entry";
       });
diff --git a/nixos/modules/services/x11/xautolock.nix b/nixos/modules/services/x11/xautolock.nix
index cbe000058dc6..10eef8aefbcd 100644
--- a/nixos/modules/services/x11/xautolock.nix
+++ b/nixos/modules/services/x11/xautolock.nix
@@ -129,7 +129,7 @@ in
           assertion = cfg.killer != null -> cfg.killtime >= 10;
           message = "killtime has to be at least 10 minutes according to `man xautolock`";
         }
-      ] ++ (lib.flip map [ "locker" "notifier" "nowlocker" "killer" ]
+      ] ++ (lib.forEach [ "locker" "notifier" "nowlocker" "killer" ]
         (option:
         {
           assertion = cfg."${option}" != null -> builtins.substring 0 1 cfg."${option}" == "/";
diff --git a/nixos/modules/services/x11/xserver.nix b/nixos/modules/services/x11/xserver.nix
index 82730c5e80c6..e716d3bcdc65 100644
--- a/nixos/modules/services/x11/xserver.nix
+++ b/nixos/modules/services/x11/xserver.nix
@@ -75,7 +75,7 @@ let
   in imap1 mkHead cfg.xrandrHeads;
 
   xrandrDeviceSection = let
-    monitors = flip map xrandrHeads (h: ''
+    monitors = forEach xrandrHeads (h: ''
       Option "monitor-${h.config.output}" "${h.name}"
     '');
     # First option is indented through the space in the config but any
diff --git a/nixos/modules/system/boot/loader/grub/grub.nix b/nixos/modules/system/boot/loader/grub/grub.nix
index 4e4d14985b0d..eca9dad64222 100644
--- a/nixos/modules/system/boot/loader/grub/grub.nix
+++ b/nixos/modules/system/boot/loader/grub/grub.nix
@@ -684,7 +684,7 @@ in
           assertion = if args.efiSysMountPoint == null then true else hasPrefix "/" args.efiSysMountPoint;
           message = "EFI paths must be absolute, not ${args.efiSysMountPoint}";
         }
-      ] ++ flip map args.devices (device: {
+      ] ++ forEach args.devices (device: {
         assertion = device == "nodev" || hasPrefix "/" device;
         message = "GRUB devices must be absolute paths, not ${device} in ${args.path}";
       }));
diff --git a/nixos/modules/tasks/network-interfaces-systemd.nix b/nixos/modules/tasks/network-interfaces-systemd.nix
index 857aaf1e6e30..fbca54978e5b 100644
--- a/nixos/modules/tasks/network-interfaces-systemd.nix
+++ b/nixos/modules/tasks/network-interfaces-systemd.nix
@@ -74,7 +74,7 @@ in
         enable = true;
         networks."99-main" = genericNetwork mkDefault;
       }
-      (mkMerge (flip map interfaces (i: {
+      (mkMerge (forEach interfaces (i: {
         netdevs = mkIf i.virtual ({
           "40-${i.name}" = {
             netdevConfig = {
@@ -90,7 +90,7 @@ in
           name = mkDefault i.name;
           DHCP = mkForce (dhcpStr
             (if i.useDHCP != null then i.useDHCP else cfg.useDHCP && interfaceIps i == [ ]));
-          address = flip map (interfaceIps i)
+          address = forEach (interfaceIps i)
             (ip: "${ip.address}/${toString ip.prefixLength}");
           networkConfig.IPv6PrivacyExtensions = "kernel";
         } ];
@@ -102,7 +102,7 @@ in
             Kind = "bridge";
           };
         };
-        networks = listToAttrs (flip map bridge.interfaces (bi:
+        networks = listToAttrs (forEach bridge.interfaces (bi:
           nameValuePair "40-${bi}" (mkMerge [ (genericNetwork (mkOverride 999)) {
             DHCP = mkOverride 0 (dhcpStr false);
             networkConfig.Bridge = name;
@@ -173,7 +173,7 @@ in
 
         };
 
-        networks = listToAttrs (flip map bond.interfaces (bi:
+        networks = listToAttrs (forEach bond.interfaces (bi:
           nameValuePair "40-${bi}" (mkMerge [ (genericNetwork (mkOverride 999)) {
             DHCP = mkOverride 0 (dhcpStr false);
             networkConfig.Bond = name;
diff --git a/nixos/modules/tasks/network-interfaces.nix b/nixos/modules/tasks/network-interfaces.nix
index f9b0eb330bf8..7c98010bd3d6 100644
--- a/nixos/modules/tasks/network-interfaces.nix
+++ b/nixos/modules/tasks/network-interfaces.nix
@@ -926,7 +926,7 @@ in
     warnings = concatMap (i: i.warnings) interfaces;
 
     assertions =
-      (flip map interfaces (i: {
+      (forEach interfaces (i: {
         # With the linux kernel, interface name length is limited by IFNAMSIZ
         # to 16 bytes, including the trailing null byte.
         # See include/linux/if.h in the kernel sources
@@ -934,12 +934,12 @@ in
         message = ''
           The name of networking.interfaces."${i.name}" is too long, it needs to be less than 16 characters.
         '';
-      })) ++ (flip map slaveIfs (i: {
+      })) ++ (forEach slaveIfs (i: {
         assertion = i.ipv4.addresses == [ ] && i.ipv6.addresses == [ ];
         message = ''
           The networking.interfaces."${i.name}" must not have any defined ips when it is a slave.
         '';
-      })) ++ (flip map interfaces (i: {
+      })) ++ (forEach interfaces (i: {
         assertion = i.preferTempAddress -> cfg.enableIPv6;
         message = ''
           Temporary addresses are only needed when IPv6 is enabled.
@@ -967,8 +967,8 @@ in
       "net.ipv6.conf.default.disable_ipv6" = mkDefault (!cfg.enableIPv6);
       "net.ipv6.conf.all.forwarding" = mkDefault (any (i: i.proxyARP) interfaces);
     } // listToAttrs (flip concatMap (filter (i: i.proxyARP) interfaces)
-        (i: flip map [ "4" "6" ] (v: nameValuePair "net.ipv${v}.conf.${i.name}.proxy_arp" true)))
-      // listToAttrs (flip map (filter (i: i.preferTempAddress) interfaces)
+        (i: forEach [ "4" "6" ] (v: nameValuePair "net.ipv${v}.conf.${i.name}.proxy_arp" true)))
+      // listToAttrs (forEach (filter (i: i.preferTempAddress) interfaces)
         (i: nameValuePair "net.ipv6.conf.${i.name}.use_tempaddr" 2));
 
     # Capabilities won't work unless we have at-least a 4.3 Linux
@@ -1051,7 +1051,7 @@ in
           ${cfg.localCommands}
         '';
       };
-    } // (listToAttrs (flip map interfaces (i:
+    } // (listToAttrs (forEach interfaces (i:
       let
         deviceDependency = if (config.boot.isContainer || i.name == "lo")
           then []
diff --git a/nixos/tests/networking.nix b/nixos/tests/networking.nix
index ed9f287d5582..ff769886c57b 100644
--- a/nixos/tests/networking.nix
+++ b/nixos/tests/networking.nix
@@ -21,7 +21,7 @@ let
         useNetworkd = networkd;
         firewall.checkReversePath = true;
         firewall.allowedUDPPorts = [ 547 ];
-        interfaces = mkOverride 0 (listToAttrs (flip map vlanIfs (n:
+        interfaces = mkOverride 0 (listToAttrs (forEach vlanIfs (n:
           nameValuePair "eth${toString n}" {
             ipv4.addresses = [ { address = "192.168.${toString n}.1"; prefixLength = 24; } ];
             ipv6.addresses = [ { address = "fd00:1234:5678:${toString n}::1"; prefixLength = 64; } ];
diff --git a/pkgs/applications/networking/irc/weechat/wrapper.nix b/pkgs/applications/networking/irc/weechat/wrapper.nix
index 6dcd9a31e5e0..5fe20829c032 100644
--- a/pkgs/applications/networking/irc/weechat/wrapper.nix
+++ b/pkgs/applications/networking/irc/weechat/wrapper.nix
@@ -54,7 +54,7 @@ let
     init = let
       init = builtins.replaceStrings [ "\n" ] [ ";" ] (config.init or "");
 
-      mkScript = drv: lib.flip map drv.scripts (script: "/script load ${drv}/share/${script}");
+      mkScript = drv: lib.forEach drv.scripts (script: "/script load ${drv}/share/${script}");
 
       scripts = builtins.concatStringsSep ";" (lib.foldl (scripts: drv: scripts ++ mkScript drv)
         [ ] (config.scripts or []));
diff --git a/pkgs/applications/networking/remote/citrix-receiver/default.nix b/pkgs/applications/networking/remote/citrix-receiver/default.nix
index d6e25ae4e7b5..45012d32f454 100644
--- a/pkgs/applications/networking/remote/citrix-receiver/default.nix
+++ b/pkgs/applications/networking/remote/citrix-receiver/default.nix
@@ -58,7 +58,7 @@ let
       versions = [ "13.8.0" "13.9.0" "13.9.1" ];
     in
       lib.listToAttrs
-        (lib.flip map versions
+        (lib.forEach versions
           (v: lib.nameValuePair v (throw "Unsupported citrix_receiver version: ${v}")));
   in
     deprecatedVersions // supportedVersions;
diff --git a/pkgs/applications/networking/remote/citrix-workspace/default.nix b/pkgs/applications/networking/remote/citrix-workspace/default.nix
index 13a16a6e2245..aa0541728aad 100644
--- a/pkgs/applications/networking/remote/citrix-workspace/default.nix
+++ b/pkgs/applications/networking/remote/citrix-workspace/default.nix
@@ -59,7 +59,7 @@ let
       versions = [ ];
     in
       lib.listToAttrs
-        (lib.flip map versions
+        (lib.forEach versions
           (v: lib.nameValuePair v (throw "Unsupported citrix_workspace version: ${v}")));
   in
     deprecatedVersions // supportedVersions;
diff --git a/pkgs/tools/inputmethods/ibus-engines/ibus-typing-booster/wrapper.nix b/pkgs/tools/inputmethods/ibus-engines/ibus-typing-booster/wrapper.nix
index 1115e4e232fc..56ddf93af45f 100644
--- a/pkgs/tools/inputmethods/ibus-engines/ibus-typing-booster/wrapper.nix
+++ b/pkgs/tools/inputmethods/ibus-engines/ibus-typing-booster/wrapper.nix
@@ -4,7 +4,7 @@
 
 let
 
-  hunspellDirs = with lib; makeSearchPath ":" (flatten (flip map langs (lang: [
+  hunspellDirs = with lib; makeSearchPath ":" (flatten (forEach langs (lang: [
     "${hunspellDicts.${lang}}/share/hunspell"
     "${hunspellDicts.${lang}}/share/myspell"
     "${hunspellDicts.${lang}}/share/myspell/dicts"

From d0413360d3a6c51dc56d4ce0ab07ad4678a83ada Mon Sep 17 00:00:00 2001
From: danbst <abcz2.uprola@gmail.com>
Date: Mon, 5 Aug 2019 14:06:20 +0300
Subject: [PATCH 5/7] rename foreach -> forEach

---
 lib/lists.nix | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/lib/lists.nix b/lib/lists.nix
index f9953720ee10..e4fcf959b60c 100644
--- a/lib/lists.nix
+++ b/lib/lists.nix
@@ -24,15 +24,15 @@ rec {
   /*  Apply the function to each element in the list. Same as `map`, but arguments
       flipped.
 
-      Type: foreach :: [a] -> (a -> b) -> [b]
+      Type: forEach :: [a] -> (a -> b) -> [b]
 
       Example:
-        foreach [ 1 2 ] (x:
+        forEach [ 1 2 ] (x:
           toString x
         )
         => [ "1" "2" ]
   */
-  foreach = xs: f: map f xs;
+  forEach = xs: f: map f xs;
 
   /* “right fold” a binary function `op` between successive elements of
      `list` with `nul' as the starting value, i.e.,

From 210c57883e659f5a1d4f5c29ed5970df93ee2940 Mon Sep 17 00:00:00 2001
From: danbst <abcz2.uprola@gmail.com>
Date: Mon, 5 Aug 2019 14:10:35 +0300
Subject: [PATCH 6/7] and one more place

---
 lib/default.nix | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/default.nix b/lib/default.nix
index f876c57e25c8..18d2dfae1e18 100644
--- a/lib/default.nix
+++ b/lib/default.nix
@@ -71,7 +71,7 @@ let
       zipAttrsWithNames zipAttrsWith zipAttrs recursiveUpdateUntil
       recursiveUpdate matchAttrs overrideExisting getOutput getBin
       getLib getDev chooseDevOutputs zipWithNames zip;
-    inherit (lists) singleton foreach foldr fold foldl foldl' imap0 imap1
+    inherit (lists) singleton forEach foldr fold foldl foldl' imap0 imap1
       concatMap flatten remove findSingle findFirst any all count
       optional optionals toList range partition zipListsWith zipLists
       reverseList listDfs toposort sort naturalSort compareLists take

From 29ba0a0adff274f5ea0d93246be3f2957d234a7b Mon Sep 17 00:00:00 2001
From: danbst <abcz2.uprola@gmail.com>
Date: Mon, 5 Aug 2019 14:34:51 +0300
Subject: [PATCH 7/7] add release notes

---
 nixos/doc/manual/release-notes/rl-1909.xml | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/nixos/doc/manual/release-notes/rl-1909.xml b/nixos/doc/manual/release-notes/rl-1909.xml
index 6f049005ab69..398234cf0251 100644
--- a/nixos/doc/manual/release-notes/rl-1909.xml
+++ b/nixos/doc/manual/release-notes/rl-1909.xml
@@ -387,6 +387,18 @@
      installer after creating <literal>/var/lib/nextcloud</literal>.
     </para>
    </listitem>
+   <listitem>
+    <para>
+     There exists now <literal>lib.forEach</literal>, which is like <literal>map</literal>, but with
+     arguments flipped. When mapping function body spans many lines (or has nested
+     <literal>map</literal>s), it is often hard to follow which list is modified.
+    </para>
+    <para>
+     Previous solution to this problem was either to use <literal>lib.flip map</literal>
+     idiom or extract that anonymous mapping function to a named one. Both can still be used
+     but <literal>lib.forEach</literal> is preferred over <literal>lib.flip map</literal>.
+    </para>
+   </listitem>
   </itemizedlist>
  </section>
 </section>