Add matrix (#489)

Author: keiravillekode

config.json

@@ -590,6 +590,14 @@
         "prerequisites": [],
         "difficulty": 4
       },
+      {
+        "slug": "matrix",
+        "name": "Matrix",
+        "uuid": "4f30e2a6-97d9-4082-a1fc-82fa8767ffe9",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 4
+      },
       {
         "slug": "nth-prime",
         "name": "Nth Prime",

exercises/practice/matrix/.docs/instructions.md

@@ -0,0 +1,38 @@
+# Instructions
+
+Given a string representing a matrix of numbers, return the rows and columns of that matrix.
+
+So given a string with embedded newlines like:
+
+```text
+9 8 7
+5 3 2
+6 6 7
+```
+
+representing this matrix:
+
+```text
+    1  2  3
+  |---------
+1 | 9  8  7
+2 | 5  3  2
+3 | 6  6  7
+```
+
+your code should be able to spit out:
+
+- A list of the rows, reading each row left-to-right while moving top-to-bottom across the rows,
+- A list of the columns, reading each column top-to-bottom while moving from left-to-right.
+
+The rows for our example matrix:
+
+- 9, 8, 7
+- 5, 3, 2
+- 6, 6, 7
+
+And its columns:
+
+- 9, 5, 6
+- 8, 3, 6
+- 7, 2, 7

exercises/practice/matrix/.meta/config.json

@@ -0,0 +1,19 @@
+{
+  "authors": [
+    "keiravillekode"
+  ],
+  "files": {
+    "solution": [
+      "matrix.el"
+    ],
+    "test": [
+      "matrix-test.el"
+    ],
+    "example": [
+      ".meta/example.el"
+    ]
+  },
+  "blurb": "Given a string representing a matrix of numbers, return the rows and columns of that matrix.",
+  "source": "Exercise by the JumpstartLab team for students at The Turing School of Software and Design.",
+  "source_url": "https://turing.edu"
+}

exercises/practice/matrix/.meta/example.el

@@ -0,0 +1,22 @@
+;;; matrix.el --- Matrix (exercism)  -*- lexical-binding: t; -*-
+
+;;; Commentary:
+
+;;; Code:
+
+(require 'seq)
+
+(defun row (string index)
+  (seq-into (mapcar #'string-to-number
+              (split-string (nth (1- index)
+                              (split-string string "\n")) " ")) 'vector))
+
+(defun column (string index)
+  (let ((extract (lambda (line)
+                   (string-to-number (nth (1- index)
+                                       (split-string line " "))))))
+    (seq-into (seq-map extract
+                (split-string string "\n")) 'vector)))
+
+(provide 'matrix)
+;;; matrix.el ends here

exercises/practice/matrix/.meta/tests.toml

@@ -0,0 +1,34 @@
+# 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.
+
+[ca733dab-9d85-4065-9ef6-a880a951dafd]
+description = "extract row from one number matrix"
+
+[5c93ec93-80e1-4268-9fc2-63bc7d23385c]
+description = "can extract row"
+
+[2f1aad89-ad0f-4bd2-9919-99a8bff0305a]
+description = "extract row where numbers have different widths"
+
+[68f7f6ba-57e2-4e87-82d0-ad09889b5204]
+description = "can extract row from non-square matrix with no corresponding column"
+
+[e8c74391-c93b-4aed-8bfe-f3c9beb89ebb]
+description = "extract column from one number matrix"
+
+[7136bdbd-b3dc-48c4-a10c-8230976d3727]
+description = "can extract column"
+
+[ad64f8d7-bba6-4182-8adf-0c14de3d0eca]
+description = "can extract column from non-square matrix with no corresponding row"
+
+[9eddfa5c-8474-440e-ae0a-f018c2a0dd89]
+description = "extract column where numbers have different widths"

exercises/practice/matrix/matrix-test.el

@@ -0,0 +1,46 @@
+;;; matrix-test.el --- Tests for Matrix (exercism)  -*- lexical-binding: t; -*-
+
+;;; Commentary:
+
+;;; Code:
+
+
+(load-file "matrix.el")
+(declare-function row "matrix.el" (string index))
+(declare-function column "matrix.el" (string index))
+
+
+(ert-deftest extract-row-from-one-number-matrix ()
+  (should (equal [1] (row "1" 1))))
+
+
+(ert-deftest can-extract-row ()
+  (should (equal [3 4] (row "1 2\n3 4" 2))))
+
+
+(ert-deftest extract-row-where-numbers-have-different-widths ()
+  (should (equal [10 20] (row "1 2\n10 20" 2))))
+
+
+(ert-deftest can-extract-row-from-non-square-matrix-with-no-corresponding-column ()
+  (should (equal [8 7 6] (row "1 2 3\n4 5 6\n7 8 9\n8 7 6" 4))))
+
+
+(ert-deftest extract-column-from-one-number-matrix ()
+  (should (equal [1] (column "1" 1))))
+
+
+(ert-deftest can-extract-column ()
+  (should (equal [3 6 9] (column "1 2 3\n4 5 6\n7 8 9" 3))))
+
+
+(ert-deftest can-extract-column-from-non-square-matrix-with-no-corresponding-row ()
+  (should (equal [4 8 6] (column "1 2 3 4\n5 6 7 8\n9 8 7 6" 4))))
+
+
+(ert-deftest extract-column-where-numbers-have-different-widths ()
+  (should (equal [1903 3 4] (column "89 1903 3\n18 3 1\n9 4 800" 2))))
+
+
+(provide 'matrix-test)
+;;; matrix-test.el ends here

exercises/practice/matrix/matrix.el

@@ -0,0 +1,16 @@
+;;; matrix.el --- Matrix (exercism)  -*- lexical-binding: t; -*-
+
+;;; Commentary:
+
+;;; Code:
+
+
+(defun row (string index)
+  (error "Delete this S-Expression and write your own implementation"))
+
+(defun column (string index)
+  (error "Delete this S-Expression and write your own implementation"))
+
+
+(provide 'matrix)
+;;; matrix.el ends here