Function

A function is a machine that takes in one thing and spits out another. [TODO gross definition]

Examples

The following table is a function:

f(x)

x	(0,0)	(1,0)	(0,1)	(1,1)
f(x)	0	1	1	0

That table describes the input and output of an XOR gate. A XOR gate (another example of a function) can also be seen in the figure.

Redstone XOR gate in Minecraft

The following lines of C++ code are a function:

string reverseString(const string &s) { 
  string returnStr = ""; 
  for (int i = s.size() - 1; i >= 0; --i) { 
    returnStr.append(s[I]);
  }
  return returnStr;
}