ensure-unit(n)
  foo bar
  foo bar
  foo bar
  n is a 'unit'

body
  a = 15
  b = 15
  
  // yes
  foo a == b and (b == 15 ? 1 : 0) ? yes : no
  
  // true
  foo a == b and b == a
  
  // yay
  foo 15px is a 'unit' and #fff is a 'color'?yay:nah
  
  // nah
  foo 15px is a 'color' and #fff is a 'color'?yay:nah
  
  // nah
  foo 15px is a 'unit' and #fff is a 'unit'?  yay   : nah
  
  // true
  foo ensure-unit(15)
  
  // false
  foo ensure-unit(#fff)