Euler question 2 sum of even fibonacci numbers

Learnt two points on this one, even though so simple. One of them has surely created a lot of errors!

When I first did this I declared the variable c but did not assign it a value before being used as part of a condition in a while loop (once in the loop was a + b). This was not spotted by the compiler but still compiled OK, then fell down and didn't work. The lesson seems to be always assign a value as soon as a variable is declared to avoid trouble spotting this type of problem later.

Second I had a warning in the syntax editor when comparing a signed and an unsigned integer. Did not cause a problem this time but easy to imagine it causing a problem in future

//============================================================================
// Name        : euler_q2_even_fibonacci.cpp
// Author      : mjl
// Version     :
// Copyright   : Your copyright notice
// Description : Hello World in C++, Ansi-style
//============================================================================

#include <iostream>
using namespace std;

int main() {

	//you can declare multiple variables of the same type on one line
	//separate by commas but ; at the end
	unsigned int a, b, c;
	a = 1;
	b = 1;

	// this did not work when I did not include the below
	//but still compiled OK!
	//Probably something to do with the use in a while statement
	//comparison before being assigned a value!
	c = 0;


	unsigned int upper_limit = 4000000;

	//use modulo to allow more for not just even numbers
	int modulo = 2;

	unsigned int answer = 0;

	//need a while loop, not a for loop
	while (c < upper_limit) {
		c = a + b;
		if (c % modulo == 0){
			answer += c;
		}
		a = b;
		b = c;
	}

	cout << "the answer is " << answer;
	return 0;
}

Project Euler question 1 fizz buzz

This worked! Learnt for loops and if statements, compound cout, signed variables.

//============================================================================
// Name        : euler_q1_fizz_buzz.cpp
// Author      : mjl
// Version     :
// Copyright   : Your copyright notice
// Description : Hello World in C++, Ansi-style
//============================================================================

#include <iostream>
using namespace std;

int main() {

	//you can create variable and assign a number at the same time
	//don't forget the ; after the variable declaration

	//don't foreget the ; inside the for loop declaration BUT...
	//you don't need a ; after the last increase statememt in the loop

	//make upper_limit unsigned for the hell of it
	unsigned int upper_limit = 1000;
	int answer = 0;

	// % and == same as python for modularity and comparison

	for (int x=1; x < upper_limit; x++) {
		if (x % 3 == 0){
			answer += x;
			continue;
		}
		if (x % 5 == 0){
			answer += x;
		}
	}

	//use a composite cout statement for the hell of it
	cout << "the answer is " << answer;

	return 0;
}

Posting code into blogger

Easiest way looks like simply cutting and pasting into this website. An example of the output is here...

//============================================================================
// Name        : euler_q1_fizz_buzz.cpp
// Author      : mjl
// Version     :
// Copyright   : Your copyright notice
// Description : Hello World in C++, Ansi-style
//============================================================================

#include <iostream>
using namespace std;

int main() {
	cout << "!!!Hello World!!!" << endl; // prints !!!Hello World!!!
	return 0;
}

Eclipse IDE set ups

Remember that each time you start a new project you also have to put some settings into the section below. This seems to have something to do with the linker, although can't remember what the linker does right now.