Merge pull request #31 from exercism/circular-buffer

Implement exercise 'circular-buffer'

config.json

@@ -468,6 +468,14 @@
         "prerequisites": [],
         "difficulty": 7
       },
+      {
+        "slug": "circular-buffer",
+        "name": "Circular Buffer",
+        "uuid": "ebb62daf-c09a-4ee6-99a1-4f68be5152e4",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 8
+      },
       {
         "slug": "minesweeper",
         "name": "Minesweeper",

config.yaml

@@ -421,6 +421,13 @@ exercises:
     prerequisites: []
     difficulty: 7
 
+  - slug: circular-buffer
+    name: Circular Buffer
+    uuid: ebb62daf-c09a-4ee6-99a1-4f68be5152e4
+    practices: []
+    prerequisites: []
+    difficulty: 8
+
   - slug: minesweeper
     name: Minesweeper
     uuid: 4e7dd5dd-a6b6-4d8c-be9c-7a5995a86de9

exercises/practice/circular-buffer/.docs/instructions.md

@@ -0,0 +1,58 @@
+# Instructions
+
+A circular buffer, cyclic buffer or ring buffer is a data structure that uses a single, fixed-size buffer as if it were connected end-to-end.
+
+A circular buffer first starts empty and of some predefined length.
+For example, this is a 7-element buffer:
+
+```text
+[ ][ ][ ][ ][ ][ ][ ]
+```
+
+Assume that a 1 is written into the middle of the buffer (exact starting location does not matter in a circular buffer):
+
+```text
+[ ][ ][ ][1][ ][ ][ ]
+```
+
+Then assume that two more elements are added — 2 & 3 — which get appended after the 1:
+
+```text
+[ ][ ][ ][1][2][3][ ]
+```
+
+If two elements are then removed from the buffer, the oldest values inside the buffer are removed.
+The two elements removed, in this case, are 1 & 2, leaving the buffer with just a 3:
+
+```text
+[ ][ ][ ][ ][ ][3][ ]
+```
+
+If the buffer has 7 elements then it is completely full:
+
+```text
+[5][6][7][8][9][3][4]
+```
+
+When the buffer is full an error will be raised, alerting the client that further writes are blocked until a slot becomes free.
+
+When the buffer is full, the client can opt to overwrite the oldest data with a forced write.
+In this case, two more elements — A & B — are added and they overwrite the 3 & 4:
+
+```text
+[5][6][7][8][9][A][B]
+```
+
+3 & 4 have been replaced by A & B making 5 now the oldest data in the buffer.
+Finally, if two elements are removed then what would be returned is 5 & 6 yielding the buffer:
+
+```text
+[ ][ ][7][8][9][A][B]
+```
+
+Because there is space available, if the client again uses overwrite to store C & D then the space where 5 & 6 were stored previously will be used not the location of 7 & 8.
+7 is still the oldest element and the buffer is once again full.
+
+```text
+[C][D][7][8][9][A][B]
+```

exercises/practice/circular-buffer/.meta/.yamlscript/exercise.mk

@@ -0,0 +1 @@
+YS_VERSION := 0.1.75

exercises/practice/circular-buffer/.meta/Makefile

@@ -0,0 +1,28 @@
+SHELL := bash
+
+BASE := $(shell pwd)
+
+export YS_VERSION := 0.1.79
+
+YS_LOCAL_PREFIX := ../../../../.local/v$(YS_VERSION)
+
+YS_LOCAL_BIN := $(YS_LOCAL_PREFIX)/bin
+
+YS_BIN := $(YS_LOCAL_BIN)/ys-$(YS_VERSION)
+
+TEST_FILE ?= $(wildcard *-test.ys)
+
+
+export PATH := $(YS_LOCAL_BIN):$(PATH)
+
+export YSPATH := $(BASE)
+
+
+default:
+
+test: $(YS_BIN)
+	prove -v $(TEST_FILE)
+
+$(YS_BIN):
+	curl -s https://yamlscript.org/install | \
+	  BIN=1 VERSION=$(YS_VERSION) PREFIX=$(YS_LOCAL_PREFIX) bash >/dev/null

exercises/practice/circular-buffer/.meta/circular-buffer-test.ys

@@ -0,0 +1,78 @@
+#!/usr/bin/env ys-0
+
+require ys::taptest: :all
+
+use: circular-buffer
+
+test::
+- name: Reading empty buffer should fail
+  code: run(1 [{"operation" "read", "should_succeed" false}])
+  want: true
+  uuid: 28268ed4-4ff3-45f3-820e-895b44d53dfa
+
+- name: Can read an item just written
+  code: run(1 [{"operation" "write", "item" 1, "should_succeed" true} {"operation" "read", "should_succeed" true, "expected" 1}])
+  want: true
+  uuid: 2e6db04a-58a1-425d-ade8-ac30b5f318f3
+
+- name: Each item may only be read once
+  code: run(1 [{"operation" "write", "item" 1, "should_succeed" true} {"operation" "read", "should_succeed" true, "expected" 1} {"operation" "read", "should_succeed" false}])
+  want: true
+  uuid: 90741fe8-a448-45ce-be2b-de009a24c144
+
+- name: Items are read in the order they are written
+  code: run(2 [{"operation" "write", "item" 1, "should_succeed" true} {"operation" "write", "item" 2, "should_succeed" true} {"operation" "read", "should_succeed" true, "expected" 1} {"operation" "read", "should_succeed" true, "expected" 2}])
+  want: true
+  uuid: be0e62d5-da9c-47a8-b037-5db21827baa7
+
+- name: Full buffer can't be written to
+  code: run(1 [{"operation" "write", "item" 1, "should_succeed" true} {"operation" "write", "item" 2, "should_succeed" false}])
+  want: true
+  uuid: 2af22046-3e44-4235-bfe6-05ba60439d38
+
+- name: A read frees up capacity for another write
+  code: run(1 [{"operation" "write", "item" 1, "should_succeed" true} {"operation" "read", "should_succeed" true, "expected" 1} {"operation" "write", "item" 2, "should_succeed" true} {"operation" "read", "should_succeed" true, "expected" 2}])
+  want: true
+  uuid: 547d192c-bbf0-4369-b8fa-fc37e71f2393
+
+- name: Read position is maintained even across multiple writes
+  code: run(3 [{"operation" "write", "item" 1, "should_succeed" true} {"operation" "write", "item" 2, "should_succeed" true} {"operation" "read", "should_succeed" true, "expected" 1} {"operation" "write", "item" 3, "should_succeed" true} {"operation" "read", "should_succeed" true, "expected" 2} {"operation" "read", "should_succeed" true, "expected" 3}])
+  want: true
+  uuid: 04a56659-3a81-4113-816b-6ecb659b4471
+
+- name: Items cleared out of buffer can't be read
+  code: run(1 [{"operation" "write", "item" 1, "should_succeed" true} {"operation" "clear"} {"operation" "read", "should_succeed" false}])
+  want: true
+  uuid: 60c3a19a-81a7-43d7-bb0a-f07242b1111f
+
+- name: Clear frees up capacity for another write
+  code: run(1 [{"operation" "write", "item" 1, "should_succeed" true} {"operation" "clear"} {"operation" "write", "item" 2, "should_succeed" true} {"operation" "read", "should_succeed" true, "expected" 2}])
+  want: true
+  uuid: 45f3ae89-3470-49f3-b50e-362e4b330a59
+
+- name: Clear does nothing on empty buffer
+  code: run(1 [{"operation" "clear"} {"operation" "write", "item" 1, "should_succeed" true} {"operation" "read", "should_succeed" true, "expected" 1}])
+  want: true
+  uuid: e1ac5170-a026-4725-bfbe-0cf332eddecd
+
+- name: Overwrite acts like write on non-full buffer
+  code: run(2 [{"operation" "write", "item" 1, "should_succeed" true} {"operation" "overwrite", "item" 2} {"operation" "read", "should_succeed" true, "expected" 1} {"operation" "read", "should_succeed" true, "expected" 2}])
+  want: true
+  uuid: 9c2d4f26-3ec7-453f-a895-7e7ff8ae7b5b
+
+- name: Overwrite replaces the oldest item on full buffer
+  code: run(2 [{"operation" "write", "item" 1, "should_succeed" true} {"operation" "write", "item" 2, "should_succeed" true} {"operation" "overwrite", "item" 3} {"operation" "read", "should_succeed" true, "expected" 2} {"operation" "read", "should_succeed" true, "expected" 3}])
+  want: true
+  uuid: 880f916b-5039-475c-bd5c-83463c36a147
+
+- name: Overwrite replaces the oldest item remaining in buffer following a read
+  code: run(3 [{"operation" "write", "item" 1, "should_succeed" true} {"operation" "write", "item" 2, "should_succeed" true} {"operation" "write", "item" 3, "should_succeed" true} {"operation" "read", "should_succeed" true, "expected" 1} {"operation" "write", "item" 4, "should_succeed" true} {"operation" "overwrite", "item" 5} {"operation" "read", "should_succeed" true, "expected" 3} {"operation" "read", "should_succeed" true, "expected" 4} {"operation" "read", "should_succeed" true, "expected" 5}])
+  want: true
+  uuid: bfecab5b-aca1-4fab-a2b0-cd4af2b053c3
+
+- name: Initial clear does not affect wrapping around
+  code: run(2 [{"operation" "clear"} {"operation" "write", "item" 1, "should_succeed" true} {"operation" "write", "item" 2, "should_succeed" true} {"operation" "overwrite", "item" 3} {"operation" "overwrite", "item" 4} {"operation" "read", "should_succeed" true, "expected" 3} {"operation" "read", "should_succeed" true, "expected" 4} {"operation" "read", "should_succeed" false}])
+  want: true
+  uuid: 9cebe63a-c405-437b-8b62-e3fdc1ecec5a
+
+done: 14

exercises/practice/circular-buffer/.meta/circular-buffer.ys

@@ -0,0 +1,49 @@
+!yamlscript/v0
+
+defn run(capacity operations):
+  buffer =: M(:B V(capacity * [nil]), :P 0)
+  reduce _ buffer operations:
+    fn(buffer op):
+      op item pass want =:
+        op.slice('operation' 'item'
+                 'should_succeed' 'expected')
+      args =:
+        condp eq op:
+          -'clear'     : -[buffer]
+          -'read'      : L(buffer pass want)
+          -'write'     : L(buffer pass item)
+          -'overwrite' : L(buffer pass item)
+      value("op-$op"): args*
+  =>: true
+
+defn op-clear(buffer):
+  M: :B V(buffer.B.# * [nil]) :P 0
+
+defn op-read(buffer pass want):
+  cell =: buffer.B.nth(buffer.P)
+  when pass:
+    when cell:nil?:
+      die: S("Can't read:\ " buffer)
+    when cell != want:
+      die: "Bad read:\ $cell != $want ($buffer)"
+  M: :B update-in(buffer.B [buffer.P] constantly(nil))
+     :P (buffer.P.++ % buffer.B.#)
+
+defn op-write(buffer pass item):
+  B P =: buffer.slice(q(B P))
+  I =:
+    reduce _ nil concat(range(P B.#) range(0 P)):
+      fn(idx i): idx || (not(B.$i) && i)
+
+  if I:
+    update-in: buffer [:B I] constantly(item)
+    when pass: die('Full buffer')
+
+defn op-overwrite(buffer pass item):
+  if some(nil? buffer.B):
+    op-write: buffer pass item
+    else:
+      buffer =:
+        update-in: buffer [:B buffer.P] constantly(item)
+      P =: buffer.P.++ % buffer.B.#
+      update-in: buffer [:P] constantly(P)

exercises/practice/circular-buffer/.meta/config.json

@@ -0,0 +1,23 @@
+{
+  "authors": [
+    "ingydotnet"
+  ],
+  "files": {
+    "solution": [
+      "circular-buffer.ys"
+    ],
+    "test": [
+      "circular-buffer-test.ys",
+      "GNUmakefile",
+      "Makefile",
+      ".yamlscript/exercise.mk",
+      ".yamlscript/exercism-ys-installer"
+    ],
+    "example": [
+      ".meta/circular-buffer.ys"
+    ]
+  },
+  "blurb": "A data structure that uses a single, fixed-size buffer as if it were connected end-to-end.",
+  "source": "Wikipedia",
+  "source_url": "https://en.wikipedia.org/wiki/Circular_buffer"
+}

exercises/practice/circular-buffer/.meta/tests.toml

@@ -0,0 +1,52 @@
+# 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.
+
+[28268ed4-4ff3-45f3-820e-895b44d53dfa]
+description = "reading empty buffer should fail"
+
+[2e6db04a-58a1-425d-ade8-ac30b5f318f3]
+description = "can read an item just written"
+
+[90741fe8-a448-45ce-be2b-de009a24c144]
+description = "each item may only be read once"
+
+[be0e62d5-da9c-47a8-b037-5db21827baa7]
+description = "items are read in the order they are written"
+
+[2af22046-3e44-4235-bfe6-05ba60439d38]
+description = "full buffer can't be written to"
+
+[547d192c-bbf0-4369-b8fa-fc37e71f2393]
+description = "a read frees up capacity for another write"
+
+[04a56659-3a81-4113-816b-6ecb659b4471]
+description = "read position is maintained even across multiple writes"
+
+[60c3a19a-81a7-43d7-bb0a-f07242b1111f]
+description = "items cleared out of buffer can't be read"
+
+[45f3ae89-3470-49f3-b50e-362e4b330a59]
+description = "clear frees up capacity for another write"
+
+[e1ac5170-a026-4725-bfbe-0cf332eddecd]
+description = "clear does nothing on empty buffer"
+
+[9c2d4f26-3ec7-453f-a895-7e7ff8ae7b5b]
+description = "overwrite acts like write on non-full buffer"
+
+[880f916b-5039-475c-bd5c-83463c36a147]
+description = "overwrite replaces the oldest item on full buffer"
+
+[bfecab5b-aca1-4fab-a2b0-cd4af2b053c3]
+description = "overwrite replaces the oldest item remaining in buffer following a read"
+
+[9cebe63a-c405-437b-8b62-e3fdc1ecec5a]
+description = "initial clear does not affect wrapping around"

exercises/practice/circular-buffer/.yamlscript/exercise.mk

@@ -0,0 +1 @@
+YS_VERSION := 0.1.75