Add exercise: isbn-verifier (#218)

* Add exercise: isbn-verifier

* Correct isbn-verifier example

* Update  `name` to header for exercise page

* Reduce indent to 2 spaces for consistency

config.json

@@ -406,6 +406,14 @@
         "prerequisites": [],
         "difficulty": 1
       },
+      {
+        "slug": "isbn-verifier",
+        "name": "ISBN Verifier",
+        "uuid": "a9880507-d14c-4fb1-8320-94c63a15b7d2",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 1
+      },
       {
         "slug": "two-fer",
         "name": "Two-Fer",

exercises/practice/isbn-verifier/.docs/instructions.md

@@ -0,0 +1,42 @@
+# Instructions
+
+The [ISBN-10 verification process][isbn-verification] is used to validate book identification numbers.
+These normally contain dashes and look like: `3-598-21508-8`
+
+## ISBN
+
+The ISBN-10 format is 9 digits (0 to 9) plus one check character (either a digit or an X only).
+In the case the check character is an X, this represents the value '10'.
+These may be communicated with or without hyphens, and can be checked for their validity by the following formula:
+
+```text
+(d₁ * 10 + d₂ * 9 + d₃ * 8 + d₄ * 7 + d₅ * 6 + d₆ * 5 + d₇ * 4 + d₈ * 3 + d₉ * 2 + d₁₀ * 1) mod 11 == 0
+```
+
+If the result is 0, then it is a valid ISBN-10, otherwise it is invalid.
+
+## Example
+
+Let's take the ISBN-10 `3-598-21508-8`.
+We plug it in to the formula, and get:
+
+```text
+(3 * 10 + 5 * 9 + 9 * 8 + 8 * 7 + 2 * 6 + 1 * 5 + 5 * 4 + 0 * 3 + 8 * 2 + 8 * 1) mod 11 == 0
+```
+
+Since the result is 0, this proves that our ISBN is valid.
+
+## Task
+
+Given a string the program should check if the provided string is a valid ISBN-10.
+Putting this into place requires some thinking about preprocessing/parsing of the string prior to calculating the check digit for the ISBN.
+
+The program should be able to verify ISBN-10 both with and without separating dashes.
+
+## Caveats
+
+Converting from strings to numbers can be tricky in certain languages.
+Now, it's even trickier since the check digit of an ISBN-10 may be 'X' (representing '10').
+For instance `3-598-21507-X` is a valid ISBN-10.
+
+[isbn-verification]: https://en.wikipedia.org/wiki/International_Standard_Book_Number

exercises/practice/isbn-verifier/.meta/config.json

@@ -0,0 +1,19 @@
+{
+  "authors": [
+    "simisc"
+  ],
+  "files": {
+    "solution": [
+      "isbn_verifier.f90"
+    ],
+    "test": [
+      "isbn_verifier_test.f90"
+    ],
+    "example": [
+      ".meta/example.f90"
+    ]
+  },
+  "blurb": "Check if a given string is a valid ISBN-10 number.",
+  "source": "Converting a string into a number and some basic processing utilizing a relatable real world example.",
+  "source_url": "https://en.wikipedia.org/wiki/International_Standard_Book_Number#ISBN-10_check_digit_calculation"
+}

exercises/practice/isbn-verifier/.meta/example.f90

@@ -0,0 +1,34 @@
+module isbn_verifier
+  implicit none
+
+contains
+
+  function isValid(isbn) result(valid)
+    character(*), intent(in) :: isbn
+    logical :: valid
+    integer :: counter, checksum, i, digit
+
+    counter = 10
+    checksum = 0
+
+    do i = 1, len_trim(isbn)
+
+      if ('0' <= isbn(i:i) .and. isbn(i:i) <= '9') then
+        digit = ichar(isbn(i:i)) - ichar('0')
+        checksum = checksum + counter * digit
+        counter = counter - 1
+      else if (isbn(i:i) == 'X' .and. counter == 1) then
+        checksum = checksum + 10
+        counter = counter - 1
+      else if (isbn(i:i) /= '-') then
+        valid = .false.
+        return
+      end if
+
+      if (counter < 0) exit
+    end do
+
+    valid = counter == 0 .and. mod(checksum, 11) == 0
+  end function isValid
+
+end module isbn_verifier

exercises/practice/isbn-verifier/.meta/tests.toml

@@ -0,0 +1,67 @@
+# 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.
+
+[0caa3eac-d2e3-4c29-8df8-b188bc8c9292]
+description = "valid isbn"
+
+[19f76b53-7c24-45f8-87b8-4604d0ccd248]
+description = "invalid isbn check digit"
+
+[4164bfee-fb0a-4a1c-9f70-64c6a1903dcd]
+description = "valid isbn with a check digit of 10"
+
+[3ed50db1-8982-4423-a993-93174a20825c]
+description = "check digit is a character other than X"
+
+[9416f4a5-fe01-4b61-a07b-eb75892ef562]
+description = "invalid check digit in isbn is not treated as zero"
+
+[c19ba0c4-014f-4dc3-a63f-ff9aefc9b5ec]
+description = "invalid character in isbn is not treated as zero"
+
+[28025280-2c39-4092-9719-f3234b89c627]
+description = "X is only valid as a check digit"
+
+[f6294e61-7e79-46b3-977b-f48789a4945b]
+description = "valid isbn without separating dashes"
+
+[185ab99b-3a1b-45f3-aeec-b80d80b07f0b]
+description = "isbn without separating dashes and X as check digit"
+
+[7725a837-ec8e-4528-a92a-d981dd8cf3e2]
+description = "isbn without check digit and dashes"
+
+[47e4dfba-9c20-46ed-9958-4d3190630bdf]
+description = "too long isbn and no dashes"
+
+[737f4e91-cbba-4175-95bf-ae630b41fb60]
+description = "too short isbn"
+
+[5458a128-a9b6-4ff8-8afb-674e74567cef]
+description = "isbn without check digit"
+
+[70b6ad83-d0a2-4ca7-a4d5-a9ab731800f7]
+description = "check digit of X should not be used for 0"
+
+[94610459-55ab-4c35-9b93-ff6ea1a8e562]
+description = "empty isbn"
+
+[7bff28d4-d770-48cc-80d6-b20b3a0fb46c]
+description = "input is 9 characters"
+
+[ed6e8d1b-382c-4081-8326-8b772c581fec]
+description = "invalid characters are not ignored after checking length"
+
+[daad3e58-ce00-4395-8a8e-e3eded1cdc86]
+description = "invalid characters are not ignored before checking length"
+
+[fb5e48d8-7c03-4bfb-a088-b101df16fdc3]
+description = "input is too long but contains a valid isbn"

exercises/practice/isbn-verifier/CMakeLists.txt

@@ -0,0 +1,71 @@
+# Get the exercise name from the current directory
+get_filename_component(exercise ${CMAKE_CURRENT_SOURCE_DIR} NAME)
+
+# Basic CMake project
+cmake_minimum_required(VERSION 3.0.0)
+
+# Name the project after the exercise
+project(${exercise} Fortran)
+
+# set debug build default
+set(CMAKE_BUILD_TYPE Debug)
+
+# Get a source filename from the exercise name by replacing -'s with _'s
+string(REPLACE "-" "_" file ${exercise})
+
+# Activate Fortran compiler warnings
+if(CMAKE_Fortran_COMPILER_ID MATCHES "Intel") # Intel fortran
+  if(WIN32)
+    set (CCMAKE_Fortran_FLAG ${CCMAKE_Fortran_FLAGS} "/warn:all")
+  else()
+    set (CMAKE_Fortran_FLAGS ${CCMAKE_Fortran_FLAGS} "-warn all")
+  endif()
+endif()
+if(CMAKE_Fortran_COMPILER_ID MATCHES "GNU") # GFrotran
+  set (CMAKE_Fortran_FLAGS ${CCMAKE_Fortran_FLAGS} "-std=f2008 -W -Wall -Wextra -pedantic -fbacktrace")
+endif()
+
+# Configure to run all the tests?
+if(${EXERCISM_RUN_ALL_TESTS})
+    add_definitions(-DEXERCISM_RUN_ALL_TESTS)
+    set(exercise_f90 ${file}_build_all.f90)
+else()
+    # if building in exercise folder add testlib
+    set(testlib_path ${CMAKE_CURRENT_SOURCE_DIR}/testlib)
+    if (NOT EXISTS ${testlib_path})
+      if (EXISTS ${CMAKE_CURRENT_SOURCE_DIR}/../../../testlib) # in git repo locally?
+        file(COPY ${CMAKE_CURRENT_SOURCE_DIR}/../../../testlib DESTINATION  ${CMAKE_CURRENT_SOURCE_DIR} PATTERN *)
+      else() # get from git with http
+        message("Downloading testlib from https://raw.githubusercontent.com/exercism/fortran/master")
+        file(MAKE_DIRECTORY ${testlib_path} )
+        file(DOWNLOAD https://raw.githubusercontent.com/exercism/fortran/master/testlib/TesterMain.f90 ${testlib_path}/TesterMain.f90 SHOW_PROGRESS)
+        file(DOWNLOAD https://raw.githubusercontent.com/exercism/fortran/master/testlib/CMakeLists.txt ${testlib_path}/CMakeLists.txt SHOW_PROGRESS)
+      endif()
+    endif()
+    # add lib to build
+    add_subdirectory(testlib)
+    include_directories(testlib ${CMAKE_CURRENT_BINARY_DIR}/testlib)
+    if(EXISTS ${CMAKE_CURRENT_SOURCE_DIR}/${file}.f90)
+        set(exercise_f90 ${file}.f90)
+    endif()
+endif()
+
+# Get test_files if exercise needs it
+file(GLOB test_files test_files/*.*)
+foreach(test_file ${test_files})
+    message("Copying ${test_file} to binary directory for example ${file}")
+    configure_file(${test_file} . COPYONLY)
+endforeach()
+
+# Build executable from sources and headers
+add_executable(${exercise} ${exercise_f90} ${file}_test.f90  )
+
+target_link_libraries(${exercise} TesterMain)
+
+include(CTest)
+
+add_test (${exercise}_test ${exercise} )
+
+# Run the tests on every build
+#add_custom_target(test_${exercise} ALL DEPENDS ${exercise} COMMAND ${exercise})
+

exercises/practice/isbn-verifier/isbn_verifier.f90

@@ -0,0 +1,13 @@
+module isbn_verifier
+  implicit none
+
+contains
+
+  function isValid(isbn) result(valid)
+    character(*), intent(in) :: isbn
+    logical :: valid
+
+    valid = isbn == "123" ! Replace this line with your implementation
+  end function isValid
+
+end module isbn_verifier

exercises/practice/isbn-verifier/isbn_verifier_test.f90

@@ -0,0 +1,86 @@
+! The tests were created from https://github.com/exercism/problem-specifications/blob/main/exercises/isbn-verifier/canonical-data.json
+
+program isbn_verifier_test_main
+  use TesterMain
+  use isbn_verifier
+  implicit none
+
+  ! Test 1: valid isbn
+  call assert_equal(.true., isValid("3-598-21508-8"), &
+    "valid isbn")
+
+  ! Test 2: invalid isbn check digit
+  call assert_equal(.false., isValid("3-598-21508-9"), &
+    "invalid isbn check digit")
+
+  ! Test 3: valid isbn with a check digit of 10
+  call assert_equal(.true., isValid("3-598-21507-X"), &
+    "valid isbn with a check digit of 10")
+
+  ! Test 4: check digit is a character other than X
+  call assert_equal(.false., isValid("3-598-21507-A"), &
+    "check digit is a character other than X")
+
+  ! Test 5: invalid check digit in isbn is not treated as zero
+  call assert_equal(.false., isValid("4-598-21507-B"), &
+    "invalid check digit in isbn is not treated as zero")
+
+  ! Test 6: invalid character in isbn is not treated as zero
+  call assert_equal(.false., isValid("3-598-P1581-X"), &
+    "invalid character in isbn is not treated as zero")
+
+  ! Test 7: X is only valid as a check digit
+  call assert_equal(.false., isValid("3-598-2X507-9"), &
+    "X is only valid as a check digit")
+
+  ! Test 8: valid isbn without separating dashes
+  call assert_equal(.true., isValid("3598215088"), &
+    "valid isbn without separating dashes")
+
+  ! Test 9: isbn without separating dashes and X as check digit
+  call assert_equal(.true., isValid("359821507X"), &
+    "isbn without separating dashes and X as check digit")
+
+  ! Test 10: isbn without check digit and dashes
+  call assert_equal(.false., isValid("359821507"), &
+    "isbn without check digit and dashes")
+
+  ! Test 11: too long isbn and no dashes
+  call assert_equal(.false., isValid("3598215078X"), &
+    "too long isbn and no dashes")
+
+  ! Test 12: too short isbn
+  call assert_equal(.false., isValid("00"), &
+    "too short isbn")
+
+  ! Test 13: isbn without check digit
+  call assert_equal(.false., isValid("3-598-21507"), &
+    "isbn without check digit")
+
+  ! Test 14: check digit of X should not be used for 0
+  call assert_equal(.false., isValid("3-598-21515-X"), &
+    "check digit of X should not be used for 0")
+
+  ! Test 15: empty isbn
+  call assert_equal(.false., isValid(""), &
+    "empty isbn")
+
+  ! Test 16: input is 9 characters
+  call assert_equal(.false., isValid("134456729"), &
+    "input is 9 characters")
+
+  ! Test 17: invalid characters are not ignored after checking length
+  call assert_equal(.false., isValid("3132P34035"), &
+    "invalid characters are not ignored after checking length")
+
+  ! Test 18: invalid characters are not ignored before checking length
+  call assert_equal(.false., isValid("3598P215088"), &
+    "invalid characters are not ignored before checking length")
+
+  ! Test 19: input is too long but contains a valid isbn
+  call assert_equal(.false., isValid("98245726788"), &
+    "input is too long but contains a valid isbn")
+
+  call test_report()
+
+end program