Created note API

Functionality:
* `note.midi(n: number or string)`: Converts a note in string form (e.g. A#4 or Gb3, will be documented on the wiki) or a given frequency into the respective MIDI code
* `note.freq(n: number or string)`: Converts a note in string form (e.g. A#4) or a given MIDI code into the respective frequency
* `note.get(n: number)`: Converts a MIDI value back into a string; if you have a frequency to convert, just use note.get(note.midi(frequency))
* `note.ticks(n: number)`: Converts note block ticks (0-24) into MIDI code (34-58, respectively) and vice-versa. Useful for use with note blocks and OpenComponents
* `note.play(tone: string or number,duration: number)`: Plays a note from a string or MIDI code via computer.beep

src/main/resources/assets/opencomputers/lua/rom/lib/note.lua

@@ -0,0 +1,120 @@
+--Provides all music notes in range of computer.beep in MIDI and frequency form
+--Author: Vexatos
+local computer = require("computer")
+
+local note = {}
+local notes = {}
+local reverseNotes = {}
+
+do
+  local tempNotes = {
+    "c",
+    "c#",
+    "d",
+    "d#",
+    "e",
+    "f",
+    "f#",
+    "g",
+    "g#",
+    "a",
+    "a#",
+    "b"
+    }
+  local sNotes = {}
+  local bNotes = {}
+
+  --Registers all possible notes in order
+  do
+    table.insert(sNotes,"a0")
+    table.insert(sNotes,"a#0")
+    table.insert(bNotes,"bb0")
+    table.insert(sNotes,"b0")
+    for i = 1,6 do
+      for _,v in ipairs(tempNotes) do
+        table.insert(sNotes,v..tostring(i))
+        if #v == 1 and v ~= "c" and v ~= "f" then
+          table.insert(bNotes,v.."b"..tostring(i))
+        end
+      end
+    end
+  end
+  for i=21,95 do
+    notes[sNotes[i-20]]=tostring(i)
+  end
+
+  do
+    for k,v in pairs(notes) do
+      reverseNotes[tonumber(v)]=k
+    end
+  end
+
+  --This is registered after reverseNotes to avoid conflicts
+  for k,v in ipairs(bNotes) do
+    notes[v]=tostring(notes[string.gsub(v,"(.)b(.)","%1%2")]-1)
+  end
+end
+
+--Converts string or frequency into MIDI code
+function note.midi(n)
+  if type(n) == "string" then
+    n = string.lower(n)
+    if tonumber(notes[n])~=nil then
+      return tonumber(notes[n])
+    else
+      error("Error: Wrong input "..tostring(n).." given to note.midi, needs to be <note>[semitone sign]<octave>, e.g. A#0 or Gb4")
+    end
+  elseif type(n) == "number" then
+    return math.floor((12*math.log(n/440,2))+69)
+  else
+    error("Error: Wrong input "..tostring(n).." given to note.midi, needs to be a number or a string")
+  end
+end
+
+--Converts String or MIDI code into frequency
+function note.freq(n)
+  if type(n) == "string" then
+    n = string.lower(n)
+    if tonumber(notes[n])~=nil then
+      return math.pow(2,(tonumber(notes[n])-69)/12)*440
+    else
+      error("Error: Wrong input "..tostring(n).." given to note.freq, needs to be <note>[semitone sign]<octave>, e.g. A#0 or Gb4",2)
+    end
+  elseif type(n) == "number" then
+    return math.pow(2,(n-69)/12)*440
+  else
+    error("Error: Wrong input "..tostring(n).." given to note.freq, needs to be a number or a string",2)
+  end
+end
+
+--Converts a MIDI value back into a string
+function note.get(n)
+  n = tonumber(n)
+  if reverseNotes[n] then
+    return string.upper(string.match(reverseNotes[n],"^(.)"))..string.gsub(reverseNotes[n],"^.(.*)","%1")
+  else
+    error("Error: Attempt to get a note for a non-exsisting MIDI code",2)
+  end
+end
+
+--Converts Note block ticks (0-24) to MIDI code (34-58) and vice-versa
+function note.ticks(n)
+  if type(n) == "number" then
+    if n>=0 and n<=24 then
+      return n+34
+    elseif n>=34 and n<=58 then
+      return n-34
+    else
+      error("Error: Wrong input "..tostring(n).." given to note.ticks, needs to be a number [0-24 or 34-58]",2)
+    end
+  else
+    error("Error: Wrong input "..tostring(n).." given to note.ticks, needs to be a number",2)
+  end
+end
+
+--Plays a tone, input is either the note as a string or the MIDI code as well as the duration of the tone
+function note.play(tone,duration)
+  computer.beep(note.freq(tone),duration)
+end
+
+return note