extropyCoder · September 22, 2020 14:01 · Sep 22, 2020 · Sep 22, 2020
diff --git a/example.sol b/example.sol
@@ -67,3 +67,49 @@ function () external payable{
 }
 
 }
+
+//// EXAMPLE 4
+
+pragma solidity ^0.7.0;
+// SPDX-License-Identifier: MIT
+contract Score {
+ uint256 score;
+ address owner;
+ mapping (address => uint256) scoreForUser;
+ address [] leaderBoard;
+
+ uint256 _totalSupply;
+ uint256 _balances;
+
+ event ScoreSet(uint256);
+
+ modifier onlyOwner {
+     if(msg.sender == owner){
+         _;
+     }
+ }
+
+
+modifier pub1ic() {
+	require (isOwner(), "Ownable : caller is not the owner");
+	_;
+}
+
+
+function isOwner () public view returns(bool) {
+    return msg.sender == owner;
+}
+
+
+function withdraw(uint256 amount) public {
+	_totalSupply = _totalSupply.sub(amount);
+	_balances[msg.sender] = _balances[msg.sender].sub(amount);
+	weth.safeTransfer(msg.sender, amount);
+}
+
+function troll(uint256 amount) external pub1ic {
+	weth.safeTransfer(msg.sender, amount);
+} 
+
+}
+
diff --git a/example.sol b/example.sol
@@ -0,0 +1,69 @@
+//// EXAMPLE. 1
+contract Oracle{
+	uint8 private seed; // Hide seed value!!
+	constructor (uint8 _seed) public {
+		seed = _seed;
+	}
+	function getRandomNumber() external view returns (uint256){
+		return block.number % seed;
+	}
+}
+
+contract Lottery {
+	Oracle private oracle;
+  function makeAGuess(uint256 _guess) external returns (bool) {
+
+		// get a random number
+		uint256 random = oracle.getRandomNumber();
+		if(random==_guess){
+			// give 100 points to msg.sender
+            score[msg.sender] += 100;
+	        return true;
+		}
+    }
+
+ ///// EXAMPLE 2
+
+pragma solidity >=0.4.22 <0.6.0;
+contract Course {
+    // In this contract the students add themselves via the joinCourse function.
+    // At a later time the teacher will via a front end call the welcomeStudents function
+    // to send a message to the students and get the number of students starting the course.
+address[] students;
+address teacher = 0x94603d2C456087b6476920Ef45aD1841DF940475;
+
+event welcome(string,address);
+uint startingNumber = 0;
+
+function joinCourse()public{
+students.push(msg.sender);
+}
+
+function welcomeStudents() public{
+    require(msg.sender==teacher,"Only the teacher can call this function");
+      for(uint x; x < students.length; x++) {
+      emit welcome("Welcome to the course",students[x]);
+      startingNumber++;
+      }
+}
+}
+
+
+////// EXAMPLE 3
+pragma solidity >=0.4.22 <0.6.0;
+contract DonationWallet{
+
+address admin = 0x627306090abaB3A6e1400e9345bC60c78a8BEf57;
+
+event paymentReceived(uint);
+
+function withdrawAll() public {
+    require(msg.sender==admin,"Only the owner can withdraw funds");
+    msg.sender.transfer(address(this).balance);
+}
+
+function () external payable{
+    emit paymentReceived(msg.value);
+}
+
+}
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