Add food-chain exercise (#174)

Co-authored-by: Glenn Jackman <glenn.jackman@gmail.com>

config.json

@@ -453,6 +453,14 @@
         "prerequisites": [],
         "difficulty": 6
       },
+      {
+        "slug": "food-chain",
+        "name": "Food Chain",
+        "uuid": "830897ff-ef28-4553-97b4-5c43396c3cdc",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 4
+      },
       {
         "slug": "binary-search",
         "name": "Binary Search",

exercises/practice/food-chain/.docs/instructions.md

@@ -0,0 +1,64 @@
+# Instructions
+
+Generate the lyrics of the song 'I Know an Old Lady Who Swallowed a Fly'.
+
+While you could copy/paste the lyrics, or read them from a file, this problem is much more interesting if you approach it algorithmically.
+
+This is a [cumulative song][cumulative-song] of unknown origin.
+
+This is one of many common variants.
+
+```text
+I know an old lady who swallowed a fly.
+I don't know why she swallowed the fly. Perhaps she'll die.
+
+I know an old lady who swallowed a spider.
+It wriggled and jiggled and tickled inside her.
+She swallowed the spider to catch the fly.
+I don't know why she swallowed the fly. Perhaps she'll die.
+
+I know an old lady who swallowed a bird.
+How absurd to swallow a bird!
+She swallowed the bird to catch the spider that wriggled and jiggled and tickled inside her.
+She swallowed the spider to catch the fly.
+I don't know why she swallowed the fly. Perhaps she'll die.
+
+I know an old lady who swallowed a cat.
+Imagine that, to swallow a cat!
+She swallowed the cat to catch the bird.
+She swallowed the bird to catch the spider that wriggled and jiggled and tickled inside her.
+She swallowed the spider to catch the fly.
+I don't know why she swallowed the fly. Perhaps she'll die.
+
+I know an old lady who swallowed a dog.
+What a hog, to swallow a dog!
+She swallowed the dog to catch the cat.
+She swallowed the cat to catch the bird.
+She swallowed the bird to catch the spider that wriggled and jiggled and tickled inside her.
+She swallowed the spider to catch the fly.
+I don't know why she swallowed the fly. Perhaps she'll die.
+
+I know an old lady who swallowed a goat.
+Just opened her throat and swallowed a goat!
+She swallowed the goat to catch the dog.
+She swallowed the dog to catch the cat.
+She swallowed the cat to catch the bird.
+She swallowed the bird to catch the spider that wriggled and jiggled and tickled inside her.
+She swallowed the spider to catch the fly.
+I don't know why she swallowed the fly. Perhaps she'll die.
+
+I know an old lady who swallowed a cow.
+I don't know how she swallowed a cow!
+She swallowed the cow to catch the goat.
+She swallowed the goat to catch the dog.
+She swallowed the dog to catch the cat.
+She swallowed the cat to catch the bird.
+She swallowed the bird to catch the spider that wriggled and jiggled and tickled inside her.
+She swallowed the spider to catch the fly.
+I don't know why she swallowed the fly. Perhaps she'll die.
+
+I know an old lady who swallowed a horse.
+She's dead, of course!
+```
+
+[cumulative-song]: https://en.wikipedia.org/wiki/Cumulative_song

exercises/practice/food-chain/.meta/config.json

@@ -0,0 +1,19 @@
+{
+  "authors": [
+    "erikschierboom"
+  ],
+  "files": {
+    "solution": [
+      "food-chain.8th"
+    ],
+    "test": [
+      "test.8th"
+    ],
+    "example": [
+      ".meta/example.8th"
+    ]
+  },
+  "blurb": "Generate the lyrics of the song 'I Know an Old Lady Who Swallowed a Fly'.",
+  "source": "Wikipedia",
+  "source_url": "https://en.wikipedia.org/wiki/There_Was_an_Old_Lady_Who_Swallowed_a_Fly"
+}

exercises/practice/food-chain/.meta/example.8th

@@ -0,0 +1,55 @@
+["fly", "spider", "bird", "cat", "dog", "goat", "cow", "horse"] constant animals
+
+{ 
+  "fly": "I don't know why she swallowed the fly. Perhaps she'll die.",
+  "spider": "It wriggled and jiggled and tickled inside her.",
+  "bird": "How absurd to swallow a bird!",
+  "cat": "Imagine that, to swallow a cat!",
+  "dog": "What a hog, to swallow a dog!",
+  "goat": "Just opened her throat and swallowed a goat!",
+  "cow": "I don't know how she swallowed a cow!",
+  "horse": "She's dead, of course!"
+} constant animal-remarks
+
+: animal \ n -- s
+  n:1- animals swap a:_@
+;
+
+: remark \ s -- s
+  animal-remarks swap m:_@
+;
+
+: verse-start \ n -- a
+  dup a:new swap
+  animal "I know an old lady who swallowed a %s." s:strfmt a:push
+  swap dup 1 n:= if drop ;then
+  animal remark a:push
+;
+
+: verse-catch \ s s -- s
+  over "spider" s:= if swap " that wriggled and jiggled and tickled inside her" s:+ swap then
+  "She swallowed the %s to catch the %s." s:strfmt
+;
+
+: verse-middle \ n -- a
+  n:1- >r animals ( a:open verse-catch ) 2 1 a:map+ 0 r> a:slice a:rev
+;
+
+: verse-end \ -- s
+  "fly" remark
+;
+
+: verse \ n -- a
+  dup a:new 
+  swap verse-start a:+ 
+  swap verse-middle a:+
+  verse-end a:push
+;
+
+: join-verses \ a -- a
+  ( swap a:len 0 n:= !if "" a:push then swap a:+ ) [] a:reduce
+;
+
+: recite \ n n -- a
+  ' verse -rot a:generate join-verses
+;

exercises/practice/food-chain/.meta/tests.toml

@@ -0,0 +1,40 @@
+# 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.
+
+[751dce68-9412-496e-b6e8-855998c56166]
+description = "fly"
+
+[6c56f861-0c5e-4907-9a9d-b2efae389379]
+description = "spider"
+
+[3edf5f33-bef1-4e39-ae67-ca5eb79203fa]
+description = "bird"
+
+[e866a758-e1ff-400e-9f35-f27f28cc288f]
+description = "cat"
+
+[3f02c30e-496b-4b2a-8491-bc7e2953cafb]
+description = "dog"
+
+[4b3fd221-01ea-46e0-825b-5734634fbc59]
+description = "goat"
+
+[1b707da9-7001-4fac-941f-22ad9c7a65d4]
+description = "cow"
+
+[3cb10d46-ae4e-4d2c-9296-83c9ffc04cdc]
+description = "horse"
+
+[22b863d5-17e4-4d1e-93e4-617329a5c050]
+description = "multiple verses"
+
+[e626b32b-745c-4101-bcbd-3b13456893db]
+description = "full song"

exercises/practice/food-chain/food-chain.8th

@@ -0,0 +1,3 @@
+: recite \ n n -- a
+
+;

exercises/practice/food-chain/libs/exercism/test

@@ -0,0 +1,173 @@
+needs console/loaded
+
+\ -----------------------------------------------------------------
+
+ns: test
+
+-1 var, test-count
+var tests-passed
+var tests-failed
+var tests-skipped
+true var, run-test
+
+\ Some utility words
+
+
+: test-passed \ s x x --   \\ test name, expected value, actual value
+    2drop
+    1 tests-passed n:+!
+    con:green con:onBlack . space " ... OK" . con:white con:onBlack cr
+;
+
+: test-skipped \ s --
+    1 tests-skipped n:+!
+    con:cyan con:onBlack . space " ... SKIPPED" . con:white con:onBlack cr
+;
+
+: test-failed \ s x x --   \\ test name, expected value, actual value
+    1 tests-failed n:+!
+    rot
+    con:red con:onBlack . space " ... FAIL" . con:white con:onBlack cr
+    "    Actual:    «" . . "»" . cr
+    "    Expected:  «" . . "»" . cr cr
+;
+
+: isword?  \ x -- x f
+   dup  >kind  ns:w   n:= 
+;
+
+: run-test? \ -- T
+   run-test @ if true else "RUN_ALL_TESTS" getenv n:>bool then
+;
+
+\ Num passed + num skipped + num failed should == num tests
+: all-tests-run? \ -- T
+    tests-passed @ tests-skipped @ tests-failed @ n:+ n:+
+    test-count @ n:=
+;
+
+\ returns true if x is a date, false otherwise
+: date? \ x -- x T
+    dup >kind ns:d n:=
+;
+
+\ adapted from 8th forum -- https://8th-dev.com/forum/index.php/topic,2745.0.html
+: eq? \ x x -- T
+   \ are the items the same kind?
+   2dup >kind swap >kind n:=
+   !if 2drop false ;then
+
+   \ same kind: try different comparators
+   number? if n:= ;then
+   string? if s:= ;then
+   array?  if ' eq? a:= 2nip ;then
+   map?    if ' eq? m:= 2nip ;then
+   date?   if d:= ;then
+
+   \ otherwise fall back to 'lazy evaluation'
+   l: =
+;
+
+: eps_eq? \ n x x -- T
+   \ are the items the same kind?
+   2dup >kind swap >kind n:=
+   !if 2drop false ;then
+   number? !if 2drop false ;then  
+   rot n:~=
+;
+
+: check-depth \ ... n -- ...
+  dup>r
+  n:1+ depth n:=
+  !if
+    con:red con:onBlack 
+    "PANIC: expected stack depth to be " . r> . cr
+    "Stack is:" . cr
+    .s cr
+    255 die
+  then
+  rdrop
+;
+
+\ -----------------------------------------------------------------
+
+\ status report at end of run
+( all-tests-run?  
+  !if con:red con:onBlack "... FAIL - not all tests completed" . con:white con:onBlack cr then
+) onexit
+
+\ Print a summary of the tests run
+( con:white con:onBlack
+  test-count   @ . space "tests planned - " .
+  tests-passed @ . space "passed - " .
+  tests-skipped @ . space "skipped - " .
+  tests-failed @ . space "failed" . cr
+) onexit
+
+\ -----------------------------------------------------------------
+\ The public-facing words
+\ -----------------------------------------------------------------
+    
+: equal? \ s x w -- | s w x --
+   run-test? !if 2drop test-skipped ;; then
+   isword? !if swap then
+   w:exec
+   3 check-depth
+   2dup             \ so test-failed can show actual and expected
+   eq? if test-passed else test-failed then
+;
+
+: approx_equal? \ s x w n -- | s w x n --
+   run-test? !if 3drop test-skipped ;; then
+   -rot isword? !if swap then
+   w:exec
+   4 check-depth
+   3dup            \ so test-failed can show actual and expected
+   eps_eq?
+   if rot drop test-passed else rot drop test-failed then
+;
+
+: true? \ s w --
+   run-test? !if drop test-skipped ;; then
+   w:exec
+   2 check-depth
+   true swap dup    \ so test-failed can show actual and expected
+   if test-passed else test-failed then 
+;
+
+: false? \ s w --
+   run-test? !if drop test-skipped ;; then
+   w:exec
+   2 check-depth
+   false swap dup    \ so test-failed can show actual and expected
+   !if test-passed else test-failed then 
+;
+
+: null? \ s w --
+   run-test? !if drop test-skipped ;; then
+   w:exec
+   2 check-depth
+   null swap dup     \ so test-failed can show actual and expected
+   G:null? nip if test-passed else test-failed then 
+;
+
+: SKIP-REST-OF-TESTS false run-test ! ;
+
+: tests \ n -- 
+    test-count ! 
+;
+
+\ Set the exit status:
+\   0 = all OK
+\   1 = not all tests were run (some error occurred)
+\   2 = some tests failed
+: end-of-tests \ --
+    all-tests-run?
+    if
+      tests-failed @ 0 n:= if 0 else 2 then
+    else
+      1
+    then
+    die
+;
+

exercises/practice/food-chain/test.8th

@@ -0,0 +1,175 @@
+"food-chain.8th" f:include
+needs exercism/test
+with: test
+10 tests
+
+"fly"
+    ( 1 1 recite )
+    [
+        "I know an old lady who swallowed a fly.", 
+        "I don't know why she swallowed the fly. Perhaps she'll die."
+    ]
+    equal?
+
+SKIP-REST-OF-TESTS
+
+"spider"
+    ( 2 2 recite )
+    [
+        "I know an old lady who swallowed a spider.",
+        "It wriggled and jiggled and tickled inside her.",
+        "She swallowed the spider to catch the fly.",
+        "I don't know why she swallowed the fly. Perhaps she'll die."
+    ]
+    equal?
+
+"bird"
+    ( 3 3 recite )
+    [
+        "I know an old lady who swallowed a bird.",
+        "How absurd to swallow a bird!",
+        "She swallowed the bird to catch the spider that wriggled and jiggled and tickled inside her.",
+        "She swallowed the spider to catch the fly.",
+        "I don't know why she swallowed the fly. Perhaps she'll die."
+    ]
+    equal?
+
+"cat"
+    ( 4 4 recite )
+    [
+        "I know an old lady who swallowed a cat.",
+        "Imagine that, to swallow a cat!",
+        "She swallowed the cat to catch the bird.",
+        "She swallowed the bird to catch the spider that wriggled and jiggled and tickled inside her.",
+        "She swallowed the spider to catch the fly.",
+        "I don't know why she swallowed the fly. Perhaps she'll die."
+    ]
+    equal?
+
+"dog"
+    ( 5 5 recite )
+    [
+        "I know an old lady who swallowed a dog.",
+        "What a hog, to swallow a dog!",
+        "She swallowed the dog to catch the cat.",
+        "She swallowed the cat to catch the bird.",
+        "She swallowed the bird to catch the spider that wriggled and jiggled and tickled inside her.",
+        "She swallowed the spider to catch the fly.",
+        "I don't know why she swallowed the fly. Perhaps she'll die."
+    ]
+    equal?
+
+"goat"
+    ( 6 6 recite )
+    [
+        "I know an old lady who swallowed a goat.",
+        "Just opened her throat and swallowed a goat!",
+        "She swallowed the goat to catch the dog.",
+        "She swallowed the dog to catch the cat.",
+        "She swallowed the cat to catch the bird.",
+        "She swallowed the bird to catch the spider that wriggled and jiggled and tickled inside her.",
+        "She swallowed the spider to catch the fly.",
+        "I don't know why she swallowed the fly. Perhaps she'll die."
+    ]
+    equal?
+
+"cow"
+    ( 7 7 recite )
+    [
+        "I know an old lady who swallowed a cow.",
+        "I don't know how she swallowed a cow!",
+        "She swallowed the cow to catch the goat.",
+        "She swallowed the goat to catch the dog.",
+        "She swallowed the dog to catch the cat.",
+        "She swallowed the cat to catch the bird.",
+        "She swallowed the bird to catch the spider that wriggled and jiggled and tickled inside her.",
+        "She swallowed the spider to catch the fly.",
+        "I don't know why she swallowed the fly. Perhaps she'll die."
+    ]
+    equal?
+
+"horse"
+    ( 8 8 recite )
+    [
+        "I know an old lady who swallowed a horse.",
+        "She's dead, of course!"
+    ]
+    equal?
+
+"multiple verses"
+    ( 1 3 recite )
+    [
+        "I know an old lady who swallowed a fly.",
+        "I don't know why she swallowed the fly. Perhaps she'll die.",
+        "",
+        "I know an old lady who swallowed a spider.",
+        "It wriggled and jiggled and tickled inside her.",
+        "She swallowed the spider to catch the fly.",
+        "I don't know why she swallowed the fly. Perhaps she'll die.",
+        "",
+        "I know an old lady who swallowed a bird.",
+        "How absurd to swallow a bird!",
+        "She swallowed the bird to catch the spider that wriggled and jiggled and tickled inside her.",
+        "She swallowed the spider to catch the fly.",
+        "I don't know why she swallowed the fly. Perhaps she'll die."
+    ]
+    equal?
+
+"full song"
+    ( 1 8 recite )
+    [
+        "I know an old lady who swallowed a fly.",
+        "I don't know why she swallowed the fly. Perhaps she'll die.",
+        "",
+        "I know an old lady who swallowed a spider.",
+        "It wriggled and jiggled and tickled inside her.",
+        "She swallowed the spider to catch the fly.",
+        "I don't know why she swallowed the fly. Perhaps she'll die.",
+        "",
+        "I know an old lady who swallowed a bird.",
+        "How absurd to swallow a bird!",
+        "She swallowed the bird to catch the spider that wriggled and jiggled and tickled inside her.",
+        "She swallowed the spider to catch the fly.",
+        "I don't know why she swallowed the fly. Perhaps she'll die.",
+        "",
+        "I know an old lady who swallowed a cat.",
+        "Imagine that, to swallow a cat!",
+        "She swallowed the cat to catch the bird.",
+        "She swallowed the bird to catch the spider that wriggled and jiggled and tickled inside her.",
+        "She swallowed the spider to catch the fly.",
+        "I don't know why she swallowed the fly. Perhaps she'll die.",
+        "",
+        "I know an old lady who swallowed a dog.",
+        "What a hog, to swallow a dog!",
+        "She swallowed the dog to catch the cat.",
+        "She swallowed the cat to catch the bird.",
+        "She swallowed the bird to catch the spider that wriggled and jiggled and tickled inside her.",
+        "She swallowed the spider to catch the fly.",
+        "I don't know why she swallowed the fly. Perhaps she'll die.",
+        "",
+        "I know an old lady who swallowed a goat.",
+        "Just opened her throat and swallowed a goat!",
+        "She swallowed the goat to catch the dog.",
+        "She swallowed the dog to catch the cat.",
+        "She swallowed the cat to catch the bird.",
+        "She swallowed the bird to catch the spider that wriggled and jiggled and tickled inside her.",
+        "She swallowed the spider to catch the fly.",
+        "I don't know why she swallowed the fly. Perhaps she'll die.",
+        "",
+        "I know an old lady who swallowed a cow.",
+        "I don't know how she swallowed a cow!",
+        "She swallowed the cow to catch the goat.",
+        "She swallowed the goat to catch the dog.",
+        "She swallowed the dog to catch the cat.",
+        "She swallowed the cat to catch the bird.",
+        "She swallowed the bird to catch the spider that wriggled and jiggled and tickled inside her.",
+        "She swallowed the spider to catch the fly.",
+        "I don't know why she swallowed the fly. Perhaps she'll die.",
+        "",
+        "I know an old lady who swallowed a horse.",
+        "She's dead, of course!"
+    ]
+    equal?
+
+end-of-tests
+;with