the existence of isolated nodes is not considered, that is, I'm taking as {V u E} the elements of the rho file.

about returning the Val type on the query functions, I have implemented the Val type in such a way that when printing (show function) the result of the queries, it will be displayed correctly.

by requirement, populate has to use IO, this forces us to return IO PG in populate, slightly deviating from the specification demands

overall, some slight deviations from the practice task demands have been implemented, as the specification is somewhat loose and teachers have pointed out it should be treated as a non-strict guideline

I have forced myself to use first-order functions in several algorithms, so the program has a more functional tune, there is also a heave use of comprehension lists, as I like to think in terms of those

the Date type is treated as a String

a (small) concession has been taken on the 120-characters long code lines so I could add some ASCII art

the practice task description asked that 'For each query evaluated users must enter the real parameters and the result must print.' but after a conversation with the responsible teacher, this requirement was dropped as long as we generated an informative test

some typos were corrected from the given test files, so if you want to replicate the test results, PLEASE EXECUTE THE SCRIPT WITH THE PROVIDED TEST FILES