C++ syntax

This lesson will show how concepts such as if statements, for loops and comparison are written in c++

Conditions:

1. If statements
   These are the building blocks of our code, they are written as: if(condition){}, for example:

   int main(){ 
   	int a = 3;
   	
   	if(a > 3){
   		cout<<"a is larger than 3";
   	}
   	return 0;
   }

2. Else:
   This block executes if our condition wasn't fulfilled: if(condition){}else{}

   int main(){ 
   	int a;
   	cin>>a;
   	
   	if(a > 3){
   		cout<<"a is larger than 3";
   	}else{
   		cout<<"a is not larget than 3";
   	}
   	return 0;
   }

3. We can combine them and create else if blocks: if(condition){} else if(condition2){}

   int main(){ 
   	int a;
   	cin>>a;
   	
   	if(a > 10){
   		cout<<"a is larger than 10";
   	}else if(a>5){
   		cout<<"a is not larget than 10, but it is larger than 5";
   	}else if(a > 2){
   		cout<<"a is not larget than 5, but it is larger than 2";
   	}else{
   		cout<<"a is not larger than 2";
   	}
   	return 0;
   }

Comparison:

When writing conditions for if statements we need to use some comparator between two values (like the > in if(a>2)).
These are all the operators that exist:

• if (a > b) - is a greater than b
• if (a < b) - is a less than b
• if (a >= b) - is a greater than or equal to b
• if (a <= b) - is a less than or equal to b
• if (a == b) - is a equal to b
• if (a != b) - is a not equal to b

The not operator ! can also be placed in front of other statements:

int main(){ 
	int a;
	cin>>a;
	
	if(!(a > 3)){
		cout<<"a is not greater than 3";
	}
	return 0;
}

We can also just put variables, if they are of the boolean type (technically we can use this for any data type but it is considered bad practice):

int main(){ 
	bool a = true;
	
	if(a){
		cout<<"a is true";
	}
	return 0;
}

Loops:

Loops repeat the code inside them until a condition is met

We have 2 main loops in c++ while() and for() they are interchangeable.

1. While loops:
   They are written like while(condition), while the condition is true, the loop will repeat itself

Example:

int main(){ 
	int i = 0; //we initialize our own counter
	
	while(i < 10){ // while i is less than 10 the loop will repeat itself
		
		cout<<i<<" ";
		i++; //We have to increase the counter to avoid endless loops
	}
	return 0;
}

Output: 0 1 2 3 4 5 6 7 8 9

2. For loops:
   They are written like for(int i=0;i<n;i++)
   We have a few things to unpack here, so:

• for() - calls the loop
• int i=0; - declares a new integer i, and sets it value to 0
• i < n; - this is the most important part, this tells our loop for how long to run for, we can treat it as while i is less than n
• i++ - This is what happens when the loop finishes, it adds 1 to the value of i

Example:

int main(){ 
	for(int i=0; i<10;i++){
		cout<<i<<" ";
	}
}

Output: 0 1 2 3 4 5 6 7 8 9