exercises: provide stubs for every exercise

.github/workflows/exercises.yml

@@ -55,3 +55,9 @@ jobs:
 
       - name: Run `check_exercises`
         run: _test/check_exercises
+
+      - name: Compile `check_stubs.nim`
+        run: nim c --styleCheck:error _test/check_stubs.nim
+
+      - name: Run `check_stubs`
+        run: _test/check_stubs

_test/check_stubs.nim

@@ -0,0 +1,55 @@
+import std/[os, osproc, strformat, strutils]
+
+iterator walkExerciseDirs: string =
+  const repoRootDir = currentSourcePath().parentDir().parentDir()
+  for exerciseKind in ["concept", "practice"]:
+    for exerciseDir in walkDirs(repoRootDir / "exercises" / exerciseKind / "*"):
+      yield exerciseDir
+
+proc checkStubs: seq[string] =
+  ## Compiles and runs the test file for every exercise, using the user-facing
+  ## solution stub.
+  ##
+  ## Returns the exercise slugs for which the corresponding test file either:
+  ##
+  ## - compiles with an error
+  ##
+  ## - runs without an error (the solution stub is supposed to fail the tests)
+  result = @[]
+  stderr.writeLine "Checking stubs..."
+  for exerciseDir in walkExerciseDirs():
+    let slug = exerciseDir.lastPathPart()
+    let testPath = exerciseDir / &"test_{slug.replace('-', '_')}.nim"
+    stderr.writeLine &"{slug}"
+    const nimOptions = "--hints:off --usenimcache --filenames:canonical " &
+                       "--spellSuggest:0 --styleCheck:error"
+    let (outpCompile, errCompile) = execCmdEx(&"nim c {nimOptions} {testPath}")
+    if errCompile == 0:
+      let (outpRun, errRun) = execCmdEx(&"nim r --hints:off {testPath}")
+      if errRun == 0:
+        stderr.write outpRun
+        stderr.writeLine &"Error: the {slug} stub passed the tests\n"
+        result.add slug
+    else:
+      stderr.writeLine outpCompile
+      result.add slug
+
+proc main =
+  let errorSlugs = checkStubs()
+  if errorSlugs.len > 0:
+    let msg = fmt"""
+
+      Error: there were {errorSlugs.len} exercises with a problematic stub:
+      {errorSlugs.join(", ")}""".unindent()
+    echo msg
+    quit 1
+  else:
+    const msg = """
+
+      Success. Every exercise has a test file and stub that:
+      - compiles without error
+      - runs with an error (we want the stub to fail the tests)""".unindent()
+    echo msg
+
+when isMainModule:
+  main()

exercises/concept/lasagna/lasagna.nim

@@ -0,0 +1,14 @@
+let expectedMinutesInOven* = 5
+
+proc remainingMinutesInOven*(actualMinutesInOven: int): int =
+  ## Returns the number of minutes that the lasagna still needs to remain in the
+  ## oven to be properly prepared.
+  discard
+
+proc preparationTimeInMinutes*(numberOfLayers: int): int =
+  ## Returns the total preparation time for a given number of layers.
+  discard
+
+proc totalTimeInMinutes*(numberOfLayers, actualMinutesInOven: int): int =
+  ## Returns the total time required to prepare the lasagna.
+  discard

exercises/practice/acronym/acronym.nim

@@ -0,0 +1,2 @@
+proc abbreviate*(s: string): string =
+  discard

exercises/practice/all-your-base/all_your_base.nim

@@ -0,0 +1,2 @@
+proc convert*(digits: openArray[int], fromBase: int, toBase: int): seq[int] =
+  discard

exercises/practice/allergies/allergies.nim

@@ -0,0 +1,9 @@
+type
+  Allergen* = enum
+    Eggs, Peanuts, Shellfish, Strawberries, Tomatoes, Chocolate, Pollen, Cats
+
+proc isAllergicTo*(score: int, allergen: Allergen): bool =
+  discard
+
+proc allergies*(score: int): set[Allergen] =
+  discard

exercises/practice/anagram/anagram.nim

@@ -0,0 +1,2 @@
+proc detectAnagrams*(word: string, candidates: openArray[string]): seq[string] =
+  discard

exercises/practice/armstrong-numbers/armstrong_numbers.nim

@@ -0,0 +1,2 @@
+proc isArmstrongNumber*(n: int): bool =
+  discard

exercises/practice/atbash-cipher/atbash_cipher.nim

@@ -0,0 +1,5 @@
+proc encode*(s: string): string =
+  discard
+
+proc decode*(s: string): string =
+  discard

exercises/practice/binary/binary.nim

@@ -0,0 +1,2 @@
+proc binary*(s: string): int =
+  discard

exercises/practice/bob/bob.nim

@@ -0,0 +1,2 @@
+proc hey*(s: string): string =
+  discard

exercises/practice/collatz-conjecture/collatz_conjecture.nim

@@ -0,0 +1,2 @@
+proc steps*(n: int): int =
+  discard

exercises/practice/crypto-square/crypto_square.nim

@@ -0,0 +1,2 @@
+proc encrypt*(s: string): string =
+  discard

exercises/practice/darts/darts.nim

@@ -0,0 +1,2 @@
+proc score*(x, y: float): int =
+  discard

exercises/practice/diamond/diamond.nim

@@ -0,0 +1,2 @@
+proc diamond*(c: char): string =
+  discard

exercises/practice/difference-of-squares/difference_of_squares.nim

@@ -0,0 +1,8 @@
+proc squareOfSum*(n: int): int =
+  discard
+
+proc sumOfSquares*(n: int): int =
+  discard
+
+proc difference*(n: int): int =
+  discard

exercises/practice/diffie-hellman/diffie_hellman.nim

@@ -0,0 +1,8 @@
+proc privateKey*(p: int): int =
+  discard
+
+proc publicKey*(p, g, a: int): int =
+  discard
+
+proc secret*(p, bPub, a: int): int =
+  discard

exercises/practice/dnd-character/dnd_character.nim

@@ -1,6 +1,12 @@
 type
   Character* = object
     strength*: int
+    dexterity*: int
+    constitution*: int
+    intelligence*: int
+    wisdom*: int
+    charisma*: int
+    hitpoints*: int
 
 proc ability*: int =
   discard

exercises/practice/etl/etl.nim

@@ -0,0 +1,4 @@
+import std/tables
+
+proc transform*(t: Table[int, seq[char]]): Table[char, int] =
+  discard

exercises/practice/gigasecond/gigasecond.nim

@@ -0,0 +1,4 @@
+import std/times
+
+proc addGigasecond*(dt: DateTime): DateTime =
+  discard

exercises/practice/grade-school/grade_school.nim

@@ -0,0 +1,22 @@
+type
+  Student* = object
+    name*: string
+    grade*: int
+
+  School* = object
+    students*: seq[Student]
+
+proc roster*(school: School): seq[string] =
+  ## Returns the names of every student in the `school`, sorted by grade then name.
+  discard
+
+proc addStudent*(school: var School, name: string, grade: int) =
+  ## Adds a student with `name` and `grade` to the `school`.
+  ##
+  ## Raises a `ValueError` if `school` already contains a student named `name`.
+  discard
+
+proc grade*(school: School, grade: int): seq[string] =
+  ## Returns the names of the students in the given `school` and `grade`, in
+  ## alphabetical order.
+  discard

exercises/practice/grains/grains.nim

@@ -0,0 +1,5 @@
+proc onSquare*(n: int): uint64 =
+  discard
+
+proc total*: uint64 =
+  discard

exercises/practice/hamming/hamming.nim

@@ -0,0 +1,2 @@
+proc distance*(a, b: string): int =
+  discard

exercises/practice/high-scores/high_scores.nim

@@ -0,0 +1,8 @@
+proc latest*(scores: openArray[int]): int =
+  discard
+
+proc personalBest*(scores: openArray[int]): int =
+  discard
+
+proc personalTopThree*(scores: openArray[int]): seq[int] =
+  discard

exercises/practice/isbn-verifier/isbn_verifier.nim

@@ -0,0 +1,2 @@
+proc isValid*(s: string): bool =
+  discard

exercises/practice/isogram/isogram.nim

@@ -0,0 +1,2 @@
+proc isIsogram*(s: string): bool =
+  discard

exercises/practice/kindergarten-garden/kindergarten_garden.nim

@@ -0,0 +1,6 @@
+type
+  Plant* = enum
+    Clover, Grass, Radishes, Violets
+
+proc plants*(garden: string, student: string): seq[Plant] =
+  discard

exercises/practice/largest-series-product/largest_series_product.nim

@@ -0,0 +1,2 @@
+proc largestProduct*(s: string, span: int): int =
+  discard

exercises/practice/leap/leap.nim

@@ -0,0 +1,2 @@
+proc isLeapYear*(year: int): bool =
+  discard

exercises/practice/luhn/luhn.nim

@@ -0,0 +1,2 @@
+proc isValid*(s: string): bool =
+  discard

exercises/practice/matching-brackets/matching_brackets.nim

@@ -0,0 +1,2 @@
+proc isPaired*(s: string): bool =
+  discard

exercises/practice/matrix/matrix.nim

@@ -0,0 +1,5 @@
+proc row*(s: string, n: int): seq[int] =
+  discard
+
+proc column*(s: string, n: int): seq[int] =
+  discard

exercises/practice/meetup/meetup.nim

@@ -0,0 +1,8 @@
+import std/times
+
+type
+  Schedule* = enum
+    Teenth, First, Second, Third, Fourth, Last
+
+proc meetup*(year: int, month: int, schedule: Schedule, day: WeekDay): string =
+  discard

exercises/practice/nth-prime/nth_prime.nim

@@ -0,0 +1,2 @@
+proc prime*(n: int): int =
+  discard

exercises/practice/nucleotide-count/nucleotide_count.nim

@@ -0,0 +1,4 @@
+import std/tables
+
+proc countDna*(s: string): CountTable[char] =
+  discard

exercises/practice/pangram/pangram.nim

@@ -0,0 +1,2 @@
+proc isPangram*(s: string): bool =
+  discard

exercises/practice/pascals-triangle/pascals_triangle.nim

@@ -0,0 +1,2 @@
+proc pascal*(n: int): seq[seq[int]] =
+  discard

exercises/practice/perfect-numbers/perfect_numbers.nim

@@ -0,0 +1,6 @@
+type
+  Classification* = enum
+    Perfect, Deficient, Abundant
+
+proc classify*(n: int): Classification =
+  discard

exercises/practice/phone-number/phone_number.nim

@@ -0,0 +1,2 @@
+proc clean*(s: string): string =
+  discard

exercises/practice/prime-factors/prime_factors.nim

@@ -0,0 +1,2 @@
+proc primeFactors*(n: int64): seq[int] =
+  discard

exercises/practice/protein-translation/protein_translation.nim

@@ -0,0 +1,2 @@
+proc translate*(s: string): seq[string] =
+  discard

exercises/practice/proverb/proverb.nim

@@ -0,0 +1,2 @@
+proc recite*(words: openArray[string]): string =
+  discard

exercises/practice/queen-attack/queen_attack.nim

@@ -0,0 +1,13 @@
+type
+  Queen* = object
+    row*: int
+    col*: int
+
+proc initQueen*(row, col: int): Queen =
+  discard
+
+proc canAttack*(white, black: Queen): bool =
+  discard
+
+proc board*(white, black: Queen): string =
+  discard

exercises/practice/raindrops/raindrops.nim

@@ -0,0 +1,2 @@
+proc convert*(n: int): string =
+  discard

exercises/practice/resistor-color-duo/resistor_color_duo.nim

@@ -0,0 +1,6 @@
+type
+  ResistorColor* = enum
+    Black, Brown, Red, Orange, Yellow, Green, Blue, Violet, Grey, White
+
+proc value*(colors: openArray[ResistorColor]): int =
+  discard

exercises/practice/resistor-color-trio/resistor_color_trio.nim

@@ -0,0 +1,6 @@
+type
+  ResistorColor* = enum
+    Black, Brown, Red, Orange, Yellow, Green, Blue, Violet, Grey, White
+
+proc label*(r: array[3, ResistorColor]): tuple[value: int, unit: string] =
+  discard

exercises/practice/resistor-color/resistor_color.nim

@@ -0,0 +1,9 @@
+type
+  ResistorColor* = enum
+    Black, Brown, Red, Orange, Yellow, Green, Blue, Violet, Grey, White
+
+proc colorCode*(color: ResistorColor): int =
+  discard
+
+proc colors*: array[0..ResistorColor.high.ord, ResistorColor] =
+  discard

exercises/practice/reverse-string/reverse_string.nim

@@ -0,0 +1,2 @@
+proc reverse*(s: string): string =
+  discard

exercises/practice/rna-transcription/rna_transcription.nim

@@ -0,0 +1,2 @@
+proc toRna*(s: string): string =
+  discard

exercises/practice/robot-name/robot_name.nim

@@ -0,0 +1,10 @@
+type
+  Name* = array[5, char]
+  Robot* = object
+    name*: Name
+
+proc makeRobot*: Robot =
+  discard
+
+proc reset*(r: var Robot) =
+  discard

exercises/practice/roman-numerals/roman_numerals.nim

@@ -0,0 +1,2 @@
+proc roman*(n: int): string =
+  discard

exercises/practice/rotational-cipher/rotational_cipher.nim

@@ -0,0 +1,2 @@
+proc rotate*(s: string, n: int): string =
+  discard

exercises/practice/run-length-encoding/run_length_encoding.nim

@@ -0,0 +1,5 @@
+proc encode*(s: string): string =
+  discard
+
+proc decode*(s: string): string =
+  discard

exercises/practice/saddle-points/saddle_points.nim

@@ -0,0 +1,2 @@
+proc saddlePoints*(matrix: seq[seq[int]]): seq[tuple[r, c: int]] =
+  discard

exercises/practice/say/say.nim

@@ -0,0 +1,2 @@
+proc say*(n: int64): string =
+  discard

exercises/practice/scale-generator/scale_generator.nim

@@ -0,0 +1,6 @@
+import std/strutils
+
+const chromaticIntervals = "m".repeat(11)
+
+proc scale*(tonic: string, intervals = chromaticIntervals): seq[string] =
+  discard

exercises/practice/scrabble-score/scrabble_score.nim

@@ -0,0 +1,2 @@
+proc score*(word: string): int =
+  discard

exercises/practice/secret-handshake/secret_handshake.nim

@@ -0,0 +1,2 @@
+proc commands*(n: int): seq[string] =
+  discard

exercises/practice/series/series.nim

@@ -0,0 +1,2 @@
+proc slices*(s: string, n: int): seq[string] =
+  discard

exercises/practice/sieve/sieve.nim

@@ -0,0 +1,2 @@
+proc primes*(limit: int): seq[int] =
+  discard

exercises/practice/space-age/space_age.nim

@@ -0,0 +1,6 @@
+type
+  Planet* = enum
+    Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune
+
+proc age*(planet: Planet, seconds: int64): float =
+  discard

exercises/practice/spiral-matrix/spiral_matrix.nim

@@ -0,0 +1,2 @@
+proc spiral*(n: static int): array[n, array[n, int]] =
+  discard

exercises/practice/sublist/sublist.nim

@@ -0,0 +1,6 @@
+type
+  Comparison* = enum
+    Unequal, Sublist, Superlist, Equal
+
+proc sublist*(a, b: openArray[int]): Comparison =
+  discard

exercises/practice/sum-of-multiples/sum_of_multiples.nim

@@ -0,0 +1,2 @@
+proc sum*(limit: int, factors: openArray[int]): int =
+  discard