4 files changed, 65 insertions, 0 deletions
diff --git a/day2/ex2-dlrow-olleh/default.nix b/day2/ex2-dlrow-olleh/default.nix
new file mode 100644
index 0000000..91bbe1f
--- /dev/null
+++ b/day2/ex2-dlrow-olleh/default.nix
@@ -0,0 +1,30 @@
+/*
+This exercise demonstrates the first workflow consisting of multiple
+steps.  We will build upon the previous example by using the string
+produced in exercise 1 as input to this workflow. You can see how other
+files can be imported and used in the construction of workflows using
+`callBionix`, which imports a file and passes it `bionix` along with
+potentially some additional arguments.
+
+Goal: fill out the stage here to reverse the string using the `rev`
+program, which reads lines on stdin and writes them to stdout with the
+characters reversed. You will need to choose exactly *which* rev you
+want to use in `buildInputs`: there are three providers available
+(busybox, toybox, utillinux) and you can try them all.
+
+Bonus: change the last line to call rev twice, thereby reversing the
+strings back to the original orientation
+*/
+{bionix}:
+with bionix; let
+  hello-world = callBionix ../ex1-hello-world {};
+
+  rev = input:
+    stage {
+      name = "rev";
+      buildInputs = [];
+      buildCommand = ''
+      '';
+    };
+in
+  rev hello-world
diff --git a/day2/ex2-dlrow-olleh/flake.lock b/day2/ex2-dlrow-olleh/flake.lock
new file mode 120000
index 0000000..981422e
--- /dev/null
+++ b/day2/ex2-dlrow-olleh/flake.lock
@@ -0,0 +1 @@
+../../common/flake.lock
+\ No newline at end of file
diff --git a/day2/ex2-dlrow-olleh/flake.nix b/day2/ex2-dlrow-olleh/flake.nix
new file mode 100755
index 0000000..bfaca96
--- /dev/null
+++ b/day2/ex2-dlrow-olleh/flake.nix
@@ -0,0 +1,20 @@
+{
+  inputs = {
+    nixpkgs.url = "github:nixos/nixpkgs";
+    bionix.url = "github:papenfusslab/bionix";
+    flake-utils.url = "github:numtide/flake-utils";
+  };
+
+  outputs = {
+    self,
+    nixpkgs,
+    bionix,
+    flake-utils,
+  }:
+    flake-utils.lib.eachDefaultSystem (system: let
+      pkgs = import nixpkgs {inherit system;};
+      bionix' = import bionix {nixpkgs = pkgs;};
+    in {
+      defaultPackage = bionix'.callBionix ./. {};
+    });
+}
diff --git a/day2/ex2-dlrow-olleh/solution.nix b/day2/ex2-dlrow-olleh/solution.nix
new file mode 100644
index 0000000..ab235fe
--- /dev/null
+++ b/day2/ex2-dlrow-olleh/solution.nix
@@ -0,0 +1,14 @@
+{bionix}:
+with bionix; let
+  hello-world = callBionix ../ex1-hello-world {};
+
+  rev = input:
+    stage {
+      name = "rev";
+      buildInputs = [pkgs.toybox];
+      buildCommand = ''
+        rev < ${input} > $out
+      '';
+    };
+in
+  rev (rev hello-world)