Floating Point visualization for Riko4 (rlua)

float.lua

local exp = 5
local frac = 3

local args = {...}
if args[1] then exp = tonumber(args[1]) end
if args[2] then frac = tonumber(args[2]) end


local bits = {0}
for i = 1, exp do
  bits[i + 1] = 0
end

for i = 1, frac do
  bits[#bits + 1] = 0
end

local cursor = 1

local function getExp()
  local bias = (2^(exp - 1)) - 1

  local pos = exp + 1
  local val = 0
  local normal = false
  for i = 1, exp do
    if bits[pos] == 1 then
      val = val + 2^(i - 1)
      normal = true
    end

    pos = pos - 1
  end

  val = val - bias

  if normal then
    return val
  else
    return 1 - bias
  end
end

local function isInf()
  for i = 1, exp do
    if bits[i + 1] == 0 then
      return false
    end
  end

  for i = 1, frac do
    if bits[i + exp + 1] == 1 then
      return "nan"
    end
  end

  return true
end

local function normal()
  for i = 1, exp do
    if bits[i + 1] == 1 then
      return true
    end
  end

  return false
end

local function isZero()
  for i = 2, #bits do
    if bits[i] == 1 then
      return false
    end
  end

  return true
end

local function gcd(x, y)
  if x == y then return x end
  if x == 0 then return y end
  if y == 0 then return x end

  if x % 2 == 0 then
    if y % 2 == 1 then
      return gcd(x / 2, y)
    else
      return gcd(x / 2, y / 2) * 2
    end
  end

  if y % 2 == 0 then
    return gcd(x, y / 2)
  end

  if x > y then
    return gcd((x - y) / 2, y)
  end

  return gcd((y - x) / 2, x)
end

local function reduce(n, d)
  if n % d == 0 then
    return n / d
  end

  local div = gcd(n, d)
  return n / div, d / div
end

local function drawBreakdown(y, pass, stn, std)
  local cx, cy = write("= " .. (bits[1] == 1 and "-" or "+"), 4, y, 16)
  local ival = isInf()

  if ival == true then
    cx = write("inf", cx, cy, 11)
  elseif ival == "nan" then
    cx = write("nan", cx, cy, 11)
  elseif pass == 1 and isZero() then
    cx = write("0", cx, cy, 16)
  elseif pass == 2 then
    local v = getExp()
    local top, bot
    if v >= 0 then
      cx = write(tostring(2^v), cx, cy, 11)
      top, bot = 2^v, 1
    else
      cx = write("1/" .. 2^(-v), cx, cy, 11)
      top, bot = 1, 2^(-v)
    end

    if not std then
      cx = write(" * " .. stn, cx, cy, 8)

      local nx, ny = reduce(stn * top, bot)
      drawBreakdown(y + 12, 3, nx, ny)
    else
      cx = write(" * " .. stn .. "/" .. std, cx, cy, 8)

      local nx, ny = reduce(stn * top, std * bot)
      drawBreakdown(y + 12, 3, nx, ny)
    end
  elseif pass == 3 then
    if std then
      cx = write(stn .. "/" .. std, cx, cy, 13)
    else
      cx = write(stn, cx, cy, 13)
    end
  else
    cx = write("2^" .. getExp(), cx, cy, 11)

    local sig = normal() and {1} or {}

    local fval = normal() and "1/1" or "0"
    for i = 1, frac do
      if bits[1 + exp + i] == 1 then
        fval = fval .. " + 1/" .. (2^i)
        sig[#sig + 1] = 2^i
      end
    end

    if pass == 1 then
      local denom = sig[#sig]

      local num = 0
      for i = 1, #sig do
        num = num + denom/sig[i]
      end

      local rn, rd = reduce(num, denom)

      if not rd then
        cx = write(" * " .. rn, cx, cy, 8)
      else
        cx = write(" * " .. rn .. "/" .. rd, cx, cy, 8)
      end

      drawBreakdown(y + 12, 2, rn, rd)
    else
      if #fval > 0 then
        cx = write(" * (" .. fval .. ")", cx, cy, 8)
      else
        cx = write(" * 0", cx, cy, 8)
      end

      drawBreakdown(y + 12, 1)
    end
  end
end

local fw = gpu.font.data.w
function _draw()
  cls()

  write(bits[1], 4, 4, 16)

  for i = 1, exp do
    write(bits[1 + i], 4+(fw+1)*(i), 4, 11)
  end

  for i = 1, frac do
    write(bits[1 + exp + i], 4+(fw+1)*(exp + i), 4, 8)
  end

  write("_", 4+(fw+1)*(cursor-1), 6)

  drawBreakdown(16)

  swap()
end

function _event(e, ...)
  if e == "key" then
    local k = ...
    if k == "left" then
      cursor = (cursor - 2) % (1 + exp + frac) + 1
    elseif k == "right" then
      cursor = cursor % (1 + exp + frac) + 1
    elseif k == "space" then
      bits[cursor] = 1 - bits[cursor]
    end
  elseif e == "char" then
    local c = ...
    if c == "1" or c == "0" then
      bits[cursor] = tonumber(c)
    end
  end
end