Solution to https://adventofcode.com/2019/day/1

adventOfCode2019Day1.u

-- Solution to https://adventofcode.com/2019/day/1 by @philip_schwarz
-- Based on following solution by @runarorama: 
-- https://gist.github.com/runarorama/21e6876bd62812b9d61a312c75ec87a3

use .base
use .base.test.internals.v1.Test forAll
use .base.Test

-- Part 1

fuelRequirement : Nat -> Nat
fuelRequirement mass = mass / 3 `drop` 2 

fuel : [Nat] -> Nat
fuel masses = 
  foldl (fuelSoFar mass -> fuelSoFar + fuelRequirement mass) 
        0 
        masses 

-- Part 2

fuelRequirementRec : Nat -> Nat
fuelRequirementRec mass = fuelRequirementTaiRec mass 0

fuelRequirementTaiRec : Nat -> Nat -> Nat
fuelRequirementTaiRec mass fuelSoFar = 
  case (fuelRequirement mass) of 
    fuel | fuel > 0 -> fuelRequirementTaiRec fuel (fuelSoFar + fuel)
    _               -> fuelSoFar 

recursiveFuel : [Nat] -> Nat
recursiveFuel masses = 
  foldl (fuelSoFar mass -> fuelSoFar + fuelRequirementRec mass) 
        0 
        masses

-- test code 

testCases1 = [(12, 2), (14, 2), (1969, 654), (100756, 33583)]
testCases2 = [(14, 2), (1969, 966), (100756, 50346)]

checkCase f tc = case tc of (i, o) -> f i == o

checkAll : (a -> b) -> [(a, b)] -> [Result]
checkAll f cases = forAll (List.size cases) (Small cases) (checkCase f)

-- tests 

test> test1 = checkAll fuelRequirement testCases1

test> answer1 = checkAll fuel [(masses, 3297626)]

test> test2 = checkAll fuelRequirementRec testCases2 

test> answer2 = checkAll recursiveFuel [(masses, 4943578)]

masses = 
   [142195,
    119326,
    57976,
    138834,
    132685,
    113092,
    88731,
    52063,
    122899,
    78681,
    117881,
    121912,
    112633,
    85163,
    145655,
    76668,
    92939,
    81941,
    62645,
    126482,
    114642,
    55588,
    95934,
    68172,
    62160,
    111109,
    141496,
    97453,
    83723,
    50309,
    82930,
    66124,
    142265,
    100066,
    147434,
    149708,
    77906,
    71147,
    76590,
    59528,
    67973,
    68187,
    135534,
    129331,
    147054,
    89062,
    63159,
    80990,
    103402,
    139627,
    87251,
    66561,
    102708,
    91307,
    121287,
    149077,
    142275,
    144917,
    98677,
    114912,
    102236,
    56147,
    130660,
    63523,
    112577,
    75086,
    136006,
    142090,
    80446,
    53900,
    144975,
    143195,
    138974,
    60145,
    132474,
    62640,
    62270,
    76275,
    62315,
    85065,
    99617,
    73579,
    97553,
    79715,
    81297,
    77342,
    142907,
    114001,
    137846,
    122398,
    71457,
    133929,
    110617,
    68928,
    56741,
    87754,
    53907,
    68322,
    85782,
    140916]