ex 4.49 - impl
ex 4.49 - explanation on output
ex 4.49 - done
ex 4.50 - done
ex 4.54 - an example, and done
4.4 - logic programming

notes about
* imperative knowledge
* mathematical knowledge
* input & output of a program
4.4 - logic programming (cont.)
logic programming, unification
4.4 - logic programming. let's proceed
4.4.1 - a plan
4.4.1 - use gprolog
4.4.1 - updating db...
all infos so far to prolog
can-do-job facts
some queries (might change job to a list?)