Course of Raku / Essentials / Associative data types / Exercises / Travel distance*

Solution: Travel distance*

The hash of hashes you find in the file distances.raku is a bit redundant but very handy data structure that you can use to get the distance between any pair of cities.

The rest of the program is a couple of nested loops to scan all the segments of the itinerary and to add up to the totals.

Code

Here is the solution where the big data set is shown only partially.

my %distance = 
    Amsterdam => {
        Athens => 3082,
        Berlin => 648,
        # . . .
    },
    # . . .
    Zurich => {
        Amsterdam => 861,
        Athens => 2449,
        # . . .
    };

my @itinerary = < Berlin Prague Vienna Zurich Paris >;

my $total = 0;
for 0 .. @itinerary.elems - 2 -> $index {
    my $from = @itinerary[$index];
    my $to = @itinerary[$index + 1];

    my $distance = %distance{$from}{$to};
    say "$from — $to: $distance km";
    $total += $distance;
}

say "Total trip: $total km";

🦋 Find the program with the whole data structure in the file travel-distance.raku.

Output

For the given itinerary, the output of the program is shown below. Try out other paths through the cities that we have in the %distance hash.

$ raku exercises/associatives/travel-distance.raku
Berlin — Prague: 354 km
Prague — Vienna: 312 km
Vienna — Zurich: 784 km
Zurich — Paris: 557 km
Total trip: 2007 km

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