Recognise pure functions
Functions that don't change anything are called "pure".
Their purity makes them
- testable
- portable
- memoizable (remembering the results of a function with a given input and just giving back the same result next time it's called with the same values)
- parallelizable
Shows a random number generator function (pure function)!!
function random(m_w, m_z) {
m_z = 36969 * (m_z & 65535) + (m_z >> 16)
m_w = 18000 * (m_w & 65535) + (m_w >> 16)
return (m_z << 16) + m_w
}
This spreads pretty evenly numbers. Shows another example that receives
console as an argument and logs something out. This is impure because it changes something in the outside. It's impure because
console is an impure function. (not parallelisable)