From 2c593a4d1a2383e6d824a2a316df2336af127f3e Mon Sep 17 00:00:00 2001
From: Manuel Araoz <manuelaraoz@gmail.com>
Date: Fri, 30 Sep 2016 13:24:25 -0300
Subject: [PATCH 1/3] add poex example

---
 contracts/examples/ProofOfExistence.sol | 32 +++++++++++++++++++++++++
 1 file changed, 32 insertions(+)
 create mode 100644 contracts/examples/ProofOfExistence.sol

diff --git a/contracts/examples/ProofOfExistence.sol b/contracts/examples/ProofOfExistence.sol
new file mode 100644
index 000000000..76df19e82
--- /dev/null
+++ b/contracts/examples/ProofOfExistence.sol
@@ -0,0 +1,32 @@
+// Proof of Existence contract, version 3
+contract ProofOfExistence3 {
+
+  mapping (bytes32 => bool) proofs;
+
+  // store a proof of existence in the contract state
+  function storeProof(bytes32 proof) {
+    proofs[proof] = true;
+  }
+
+  // calculate and store the proof for a document
+  function notarize(string document) {
+    var proof = calculateProof(document);
+    storeProof(proof);
+  }
+
+  // helper function to get a document's sha256
+  function calculateProof(string document) returns (bytes32) {
+    return sha256(document);
+  }
+
+  // check if a document has been notarized
+  function checkDocument(string document) returns (bool) {
+    var proof = calculateProof(document);
+    return hasProof(proof);
+  }
+
+  // returns true if proof is stored
+  function hasProof(bytes32 proof) returns (bool) {
+    return proofs[proof];
+  }
+}

From fd45473367921588dbf5dd460742ab41d4b00d56 Mon Sep 17 00:00:00 2001
From: Manuel Araoz <manuelaraoz@gmail.com>
Date: Fri, 30 Sep 2016 13:29:34 -0300
Subject: [PATCH 2/3] minor mods to poex contract

---
 contracts/examples/ProofOfExistence.sol | 9 +++++++--
 migrations/2_deploy_contracts.js        | 1 +
 2 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/contracts/examples/ProofOfExistence.sol b/contracts/examples/ProofOfExistence.sol
index 76df19e82..626ae015c 100644
--- a/contracts/examples/ProofOfExistence.sol
+++ b/contracts/examples/ProofOfExistence.sol
@@ -1,5 +1,10 @@
-// Proof of Existence contract, version 3
-contract ProofOfExistence3 {
+import "../Rejector.sol";
+
+/*
+ * Proof of Existence example contract
+ * see https://medium.com/zeppelin-blog/the-hitchhikers-guide-to-smart-contracts-in-ethereum-848f08001f05
+ */
+contract ProofOfExistence is Rejector {
 
   mapping (bytes32 => bool) proofs;
 
diff --git a/migrations/2_deploy_contracts.js b/migrations/2_deploy_contracts.js
index 8db14c0b9..b29a532cc 100644
--- a/migrations/2_deploy_contracts.js
+++ b/migrations/2_deploy_contracts.js
@@ -1,6 +1,7 @@
 module.exports = function(deployer) {
   deployer.deploy(PullPaymentBid);
   deployer.deploy(BadArrayUse);
+  deployer.deploy(ProofOfExistence);
   deployer.deploy(Bounty);
   deployer.deploy(Ownable);
   deployer.deploy(LimitFunds);

From c7f74555a3e1fb32d6c487fd14fd1a249270d286 Mon Sep 17 00:00:00 2001
From: Manuel Araoz <manuelaraoz@gmail.com>
Date: Fri, 30 Sep 2016 13:45:55 -0300
Subject: [PATCH 3/3] add some modifiers to poex example

---
 contracts/examples/ProofOfExistence.sol | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/contracts/examples/ProofOfExistence.sol b/contracts/examples/ProofOfExistence.sol
index 626ae015c..e12382e43 100644
--- a/contracts/examples/ProofOfExistence.sol
+++ b/contracts/examples/ProofOfExistence.sol
@@ -6,7 +6,7 @@ import "../Rejector.sol";
  */
 contract ProofOfExistence is Rejector {
 
-  mapping (bytes32 => bool) proofs;
+  mapping (bytes32 => bool) public proofs;
 
   // store a proof of existence in the contract state
   function storeProof(bytes32 proof) {
@@ -20,18 +20,18 @@ contract ProofOfExistence is Rejector {
   }
 
   // helper function to get a document's sha256
-  function calculateProof(string document) returns (bytes32) {
+  function calculateProof(string document) constant returns (bytes32) {
     return sha256(document);
   }
 
   // check if a document has been notarized
-  function checkDocument(string document) returns (bool) {
+  function checkDocument(string document) constant returns (bool) {
     var proof = calculateProof(document);
     return hasProof(proof);
   }
 
   // returns true if proof is stored
-  function hasProof(bytes32 proof) returns (bool) {
+  function hasProof(bytes32 proof) constant returns (bool) {
     return proofs[proof];
   }
 }