Shopping Rules

A coffee costs 2 Euros

A tea costs 3 Euros

input(How much is a $coffee)
  && fact(A $coffee costs $x euros)
  => output($x Euros)

input(How much is a $coffee and a $tea)
  && fact(A $coffee costs $x euros)
  && fact(A $tea costs $y euros)
  && $z = eval(formatDouble(parseDouble($x) + parseDouble($y), 2))
  => output($z Euros)