Add List-Ops practice exercise

config.json

@@ -258,6 +258,14 @@
         "prerequisites": [],
         "difficulty": 3
       },
+      {
+        "slug": "list-ops",
+        "name": "List Ops",
+        "uuid": "e6e4e258-e669-4875-afce-c6a65405b3d0",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 3
+      },
       {
         "slug": "matrix",
         "name": "Matrix",

exercises/practice/difference-of-squares/.approaches/config.json

@@ -1,7 +1,8 @@
 {
   "introduction": {
-    "authors": ["oxe-i"],
-    "contributors": []
+    "authors": [
+      "oxe-i"
+    ]
   },
   "approaches": [
     {

exercises/practice/list-ops/.docs/instructions.md

@@ -0,0 +1,19 @@
+# Instructions
+
+Implement basic list operations.
+
+In functional languages list operations like `length`, `map`, and `reduce` are very common.
+Implement a series of basic list operations, without using existing functions.
+
+The precise number and names of the operations to be implemented will be track dependent to avoid conflicts with existing names, but the general operations you will implement include:
+
+- `append` (_given two lists, add all items in the second list to the end of the first list_);
+- `concatenate` (_given a series of lists, combine all items in all lists into one flattened list_);
+- `filter` (_given a predicate and a list, return the list of all items for which `predicate(item)` is True_);
+- `length` (_given a list, return the total number of items within it_);
+- `map` (_given a function and a list, return the list of the results of applying `function(item)` on all items_);
+- `foldl` (_given a function, a list, and initial accumulator, fold (reduce) each item into the accumulator from the left_);
+- `foldr` (_given a function, a list, and an initial accumulator, fold (reduce) each item into the accumulator from the right_);
+- `reverse` (_given a list, return a list with all the original items, but in reversed order_).
+
+Note, the ordering in which arguments are passed to the fold functions (`foldl`, `foldr`) is significant.

exercises/practice/list-ops/.meta/Example.lean

@@ -0,0 +1,44 @@
+namespace ListOps
+
+def append (list1 : List α) (list2 : List α) : List α :=
+  match list1 with
+  | [] => list2
+  | x :: xs => x :: append xs list2
+
+def concat (lists : List (List α)) : List α :=
+  match lists with
+  | [] => []
+  | xs :: rest => append xs (concat rest)
+
+def filter (f : α → Bool) (list : List α) : List α :=
+  match list with
+  | [] => []
+  | x :: xs => if f x then x :: filter f xs else filter f xs
+
+def length (list : List α) : Nat :=
+  match list with
+  | [] => 0
+  | _ :: xs => 1 + length xs
+
+def map (f : α → β) (list : List α) : List β :=
+  match list with
+  | [] => []
+  | x :: xs => f x :: map f xs
+
+def foldl (f : β → α → β) (initial : β) (list : List α) : β :=
+  match list with
+  | [] => initial
+  | x :: xs => foldl f (f initial x) xs
+
+def foldr (f : α → β → β) (initial : β) (list : List α) : β :=
+  match list with
+  | [] => initial
+  | x :: xs => f x (foldr f initial xs)
+
+def reverse (list : List α) : List α :=
+  let rec go (acc : List α) : List α → List α
+    | [] => acc
+    | x :: xs => go (x :: acc) xs
+  go [] list
+
+end ListOps

exercises/practice/list-ops/.meta/config.json

@@ -0,0 +1,18 @@
+{
+  "authors": [
+    "jojo8356"
+  ],
+  "files": {
+    "solution": [
+      "ListOps.lean"
+    ],
+    "test": [
+      "ListOpsTest.lean"
+    ],
+    "example": [
+      ".meta/Example.lean"
+    ]
+  },
+  "blurb": "Implement basic list operations.",
+  "source": "https://github.com/exercism/problem-specifications/tree/main/exercises/list-ops"
+}

exercises/practice/list-ops/.meta/tests.toml

@@ -0,0 +1,106 @@
+# This is an auto-generated file.
+#
+# Regenerating this file via `configlet sync` will:
+# - Recreate every `description` key/value pair
+# - Recreate every `reimplements` key/value pair, where they exist in problem-specifications
+# - Remove any `include = true` key/value pair (an omitted `include` key implies inclusion)
+# - Preserve any other key/value pair
+#
+# As user-added comments (using the # character) will be removed when this file
+# is regenerated, comments can be added via a `comment` key.
+
+[485b9452-bf94-40f7-a3db-c3cf4850066a]
+description = "append entries to a list and return the new list -> empty lists"
+
+[2c894696-b609-4569-b149-8672134d340a]
+description = "append entries to a list and return the new list -> list to empty list"
+
+[e842efed-3bf6-4295-b371-4d67a4fdf19c]
+description = "append entries to a list and return the new list -> empty list to list"
+
+[71dcf5eb-73ae-4a0e-b744-a52ee387922f]
+description = "append entries to a list and return the new list -> non-empty lists"
+
+[28444355-201b-4af2-a2f6-5550227bde21]
+description = "concatenate a list of lists -> empty list"
+
+[331451c1-9573-42a1-9869-2d06e3b389a9]
+description = "concatenate a list of lists -> list of lists"
+
+[d6ecd72c-197f-40c3-89a4-aa1f45827e09]
+description = "concatenate a list of lists -> list of nested lists"
+
+[0524fba8-3e0f-4531-ad2b-f7a43da86a16]
+description = "filter list returning only values that satisfy the filter function -> empty list"
+
+[88494bd5-f520-4edb-8631-88e415b62d24]
+description = "filter list returning only values that satisfy the filter function -> non-empty list"
+
+[1cf0b92d-8d96-41d5-9c21-7b3c37cb6aad]
+description = "returns the length of a list -> empty list"
+
+[d7b8d2d9-2d16-44c4-9a19-6e5f237cb71e]
+description = "returns the length of a list -> non-empty list"
+
+[c0bc8962-30e2-4bec-9ae4-668b8ecd75aa]
+description = "return a list of elements whose values equal the list value transformed by the mapping function -> empty list"
+
+[11e71a95-e78b-4909-b8e4-60cdcaec0e91]
+description = "return a list of elements whose values equal the list value transformed by the mapping function -> non-empty list"
+
+[613b20b7-1873-4070-a3a6-70ae5f50d7cc]
+description = "folds (reduces) the given list from the left with a function -> empty list"
+include = false
+
+[e56df3eb-9405-416a-b13a-aabb4c3b5194]
+description = "folds (reduces) the given list from the left with a function -> direction independent function applied to non-empty list"
+include = false
+
+[d2cf5644-aee1-4dfc-9b88-06896676fe27]
+description = "folds (reduces) the given list from the left with a function -> direction dependent function applied to non-empty list"
+
+[36549237-f765-4a4c-bfd9-5d3a8f7b07d2]
+description = "folds (reduces) the given list from the left with a function -> empty list"
+reimplements = "613b20b7-1873-4070-a3a6-70ae5f50d7cc"
+
+[7a626a3c-03ec-42bc-9840-53f280e13067]
+description = "folds (reduces) the given list from the left with a function -> direction independent function applied to non-empty list"
+reimplements = "e56df3eb-9405-416a-b13a-aabb4c3b5194"
+
+[d7fcad99-e88e-40e1-a539-4c519681f390]
+description = "folds (reduces) the given list from the left with a function -> direction dependent function applied to non-empty list"
+reimplements = "d2cf5644-aee1-4dfc-9b88-06896676fe27"
+include = false
+
+[aeb576b9-118e-4a57-a451-db49fac20fdc]
+description = "folds (reduces) the given list from the right with a function -> empty list"
+include = false
+
+[c4b64e58-313e-4c47-9c68-7764964efb8e]
+description = "folds (reduces) the given list from the right with a function -> direction independent function applied to non-empty list"
+include = false
+
+[be396a53-c074-4db3-8dd6-f7ed003cce7c]
+description = "folds (reduces) the given list from the right with a function -> direction dependent function applied to non-empty list"
+
+[17214edb-20ba-42fc-bda8-000a5ab525b0]
+description = "folds (reduces) the given list from the right with a function -> empty list"
+reimplements = "aeb576b9-118e-4a57-a451-db49fac20fdc"
+
+[e1c64db7-9253-4a3d-a7c4-5273b9e2a1bd]
+description = "folds (reduces) the given list from the right with a function -> direction independent function applied to non-empty list"
+reimplements = "c4b64e58-313e-4c47-9c68-7764964efb8e"
+
+[8066003b-f2ff-437e-9103-66e6df474844]
+description = "folds (reduces) the given list from the right with a function -> direction dependent function applied to non-empty list"
+reimplements = "be396a53-c074-4db3-8dd6-f7ed003cce7c"
+include = false
+
+[94231515-050e-4841-943d-d4488ab4ee30]
+description = "reverse the elements of the list -> empty list"
+
+[fcc03d1e-42e0-4712-b689-d54ad761f360]
+description = "reverse the elements of the list -> non-empty list"
+
+[40872990-b5b8-4cb8-9085-d91fc0d05d26]
+description = "reverse the elements of the list -> list of lists is not flattened"

exercises/practice/list-ops/ListOps.lean

@@ -0,0 +1,27 @@
+namespace ListOps
+
+def append (list1 : List α) (list2 : List α) : List α :=
+  sorry --remove this line and implement the function
+
+def concat (lists : List (List α)) : List α :=
+  sorry --remove this line and implement the function
+
+def filter (f : α → Bool) (list : List α) : List α :=
+  sorry --remove this line and implement the function
+
+def length (list : List α) : Nat :=
+  sorry --remove this line and implement the function
+
+def map (f : α → β) (list : List α) : List β :=
+  sorry --remove this line and implement the function
+
+def foldl (f : β → α → β) (initial : β) (list : List α) : β :=
+  sorry --remove this line and implement the function
+
+def foldr (f : α → β → β) (initial : β) (list : List α) : β :=
+  sorry --remove this line and implement the function
+
+def reverse (list : List α) : List α :=
+  sorry --remove this line and implement the function
+
+end ListOps

exercises/practice/list-ops/ListOpsTest.lean

@@ -0,0 +1,54 @@
+import LeanTest
+import ListOps
+
+open LeanTest
+
+def listOpsTests : TestSuite :=
+  (TestSuite.empty "ListOps")
+  |>.addTest "append entries to a list and return the new list -> empty lists" (do
+      return assertEqual ([] : List Int) (ListOps.append [] []))
+  |>.addTest "append entries to a list and return the new list -> list to empty list" (do
+      return assertEqual [1, 2, 3, 4] (ListOps.append ([] : List Int) [1, 2, 3, 4]))
+  |>.addTest "append entries to a list and return the new list -> empty list to list" (do
+      return assertEqual [1, 2, 3, 4] (ListOps.append [1, 2, 3, 4] ([] : List Int)))
+  |>.addTest "append entries to a list and return the new list -> non-empty lists" (do
+      return assertEqual [1, 2, 2, 3, 4, 5] (ListOps.append [1, 2] [2, 3, 4, 5]))
+  |>.addTest "concatenate a list of lists -> empty list" (do
+      return assertEqual ([] : List Int) (ListOps.concat ([] : List (List Int))))
+  |>.addTest "concatenate a list of lists -> list of lists" (do
+      return assertEqual [1, 2, 3, 4, 5, 6] (ListOps.concat [[1, 2], [3], [], [4, 5, 6]]))
+  |>.addTest "concatenate a list of lists -> list of nested lists" (do
+      return assertEqual [[1], [2], [3], [], [4, 5, 6]] (ListOps.concat [[[1], [2]], [[3]], [[]], [[4, 5, 6]]]))
+  |>.addTest "filter list returning only values that satisfy the filter function -> empty list" (do
+      return assertEqual ([] : List Int) (ListOps.filter (fun x => x % 2 == 1) []))
+  |>.addTest "filter list returning only values that satisfy the filter function -> non-empty list" (do
+      return assertEqual [1, 3, 5] (ListOps.filter (fun x => x % 2 == 1) [1, 2, 3, 5]))
+  |>.addTest "returns the length of a list -> empty list" (do
+      return assertEqual 0 (ListOps.length ([] : List Int)))
+  |>.addTest "returns the length of a list -> non-empty list" (do
+      return assertEqual 4 (ListOps.length [1, 2, 3, 4]))
+  |>.addTest "return a list of elements whose values equal the list value transformed by the mapping function -> empty list" (do
+      return assertEqual ([] : List Int) (ListOps.map (· + 1) ([] : List Int)))
+  |>.addTest "return a list of elements whose values equal the list value transformed by the mapping function -> non-empty list" (do
+      return assertEqual [2, 4, 6, 8] (ListOps.map (· + 1) [1, 3, 5, 7]))
+  |>.addTest "folds (reduces) the given list from the left with a function -> empty list" (do
+      return assertEqual 2 (ListOps.foldl (fun acc el => el * acc) 2 ([] : List Int)))
+  |>.addTest "folds (reduces) the given list from the left with a function -> direction independent function applied to non-empty list" (do
+      return assertEqual 15 (ListOps.foldl (fun acc el => el + acc) 5 [1, 2, 3, 4]))
+  |>.addTest "folds (reduces) the given list from the left with a function -> direction dependent function applied to non-empty list" (do
+      return assertEqual 0 (ListOps.foldl (· / ·) 5 [2, 5]))
+  |>.addTest "folds (reduces) the given list from the right with a function -> empty list" (do
+      return assertEqual 2 (ListOps.foldr (fun el acc => el * acc) 2 ([] : List Int)))
+  |>.addTest "folds (reduces) the given list from the right with a function -> direction independent function applied to non-empty list" (do
+      return assertEqual 15 (ListOps.foldr (fun el acc => el + acc) 5 [1, 2, 3, 4]))
+  |>.addTest "folds (reduces) the given list from the right with a function -> direction dependent function applied to non-empty list" (do
+      return assertEqual 2 (ListOps.foldr (· / ·) 5 [2, 5]))
+  |>.addTest "reverse the elements of the list -> empty list" (do
+      return assertEqual ([] : List Int) (ListOps.reverse ([] : List Int)))
+  |>.addTest "reverse the elements of the list -> non-empty list" (do
+      return assertEqual [7, 5, 3, 1] (ListOps.reverse [1, 3, 5, 7]))
+  |>.addTest "reverse the elements of the list -> list of lists is not flattened" (do
+      return assertEqual [[4, 5, 6], [], [3], [1, 2]] (ListOps.reverse [[1, 2], [3], [], [4, 5, 6]]))
+
+def main : IO UInt32 := do
+  runTestSuitesWithExitCode [listOpsTests]

exercises/practice/list-ops/lakefile.toml

@@ -0,0 +1,15 @@
+name = "list-ops"
+version = "0.1.0"
+defaultTargets = ["ListOpsTest"]
+testDriver = "ListOpsTest"
+
+[[lean_lib]]
+name = "LeanTest"
+srcDir = "vendor/LeanTest"
+
+[[lean_lib]]
+name = "ListOps"
+
+[[lean_exe]]
+name = "ListOpsTest"
+root = "ListOpsTest"

exercises/practice/list-ops/lean-toolchain

@@ -0,0 +1 @@
+leanprover/lean4:v4.25.2

exercises/practice/list-ops/vendor/LeanTest/LeanTest.lean

@@ -0,0 +1,4 @@
+-- This module serves as the root of the `LeanTest` library.
+-- Import modules here that should be built as part of the library.
+import LeanTest.Assertions
+import LeanTest.Test