TidalCycles prompt live monitor, see e.g. https://www.youtube.com/watch?v=_N0cikVFu-o

readme.md

How CycleMonitor Works

This module creates a background thread that continuously prints timing/cycle information to the terminal.

Core Functions

1. streamGetnowMods - Gets the current cycle position and calculates where you are within multiple time subdivisions (mod, mod×2, mod×4, mod×8, mod×16, mod×32):

streamGetnowMods :: Double -> Stream -> IO [Double]
streamGetnowMods mod s = do
  let mods = take 6 $ iterate (*2) mod
  result <- streamGetnow s
  return $! map (mod' result) mods

2. streamGetnowModsString - Formats this into a readable string like c:35 | 1/8 3/16 7/32...:

streamGetnowModsString :: Double -> Stream -> IO String
streamGetnowModsString mod s = do
  let mods = take 6 $ iterate (*2) mod
  results <- streamGetnowMods mod s
  cyclePos <- streamGetnow s
  let formattedResults = printf "c:%.0f |" (cyclePos+1) : zipWith (\x y -> printf "%d/%.0f" (floor x + 1) y) results mods
  return $ unwords formattedResults

3. printEverySecond - The main loop that prints BPM + cycle position. Despite the name, it actually delays based on CPS (cycles per second), so it updates roughly once per cycle:

printEverySecond :: Double -> Stream -> IO ()
printEverySecond mod s = CM.forever $ do
    result <- streamGetnowModsString mod s
    bpm <- getbpm s
    let bpmString = "t:" ++ printf "%.2f" bpm
    cps <- streamGetcps s
    let delay = floor (1 / cps * 1000000) -- convert cps to microseconds
    threadDelay delay
    putStrLn (bpmString ++ " | " ++ result)

How It's Started/Stopped

startPrinting spawns a background thread using forkIO and returns an MVar (a thread-safe variable) for control:

startPrinting :: Double -> Stream -> IO (MVar ())
startPrinting mod s = do
    stopVar <- newEmptyMVar
    _ <- forkIO $ do
        let loop = do
                stopped <- tryTakeMVar stopVar
                CM.when (stopped == Nothing) $ do
                    printEverySecond mod s
                    loop
        loop
    return stopVar

stopPrinting signals the thread to stop by putting a value in the MVar:

stopPrinting :: MVar () -> IO ()
stopPrinting stopVar = do
    putMVar stopVar ()
    return ()

Usage Pattern

To use it in your boot/session:

-- Start monitoring (8 = base cycle subdivision)
monitor <- startPrinting 8 stream

-- Later, to stop:
stopPrinting monitor

The output looks like: t:120.00 | c:35 | 1/8 3/16 7/32 15/64 31/128 63/256

This tells you the BPM, current cycle number, and your position within increasingly longer cycle periods (useful for tracking where you are in longer structural patterns like ur patterns).

CycleMonitor.hs

-- Research VSCode plugin/sidebar?
-- https://code.visualstudio.com/api/references/vscode-api#StatusBarItem
-- https://github.com/microsoft/vscode-extension-samples/blob/main/statusbar-sample/src/extension.ts
-- https://github.com/tidalcycles/vscode-tidalcycles/blob/master/src/main.ts

-- t:120 | l0 . c:0 . 190_operon(1,2,5 | pc,bd,syn): [35/64, -29 | 1:20s, 50s]

-- TODO:
--   Link clients
--   streamIDs/pattern names
--   elapsed / remaining of current ur patterns (in cycles and seconds)
--   track names
--   fft sparkline?
--   mods: Unicode fractions? Custom glyphs/random emojis?
--   intech grid values (not raw MIDI but transformed val, e.g. fast/nudge amounts)
--   set index, track names

:{
import Data.Fixed (mod')
import Text.Printf (printf)
import Control.Concurrent
import Control.Monad hiding (when)
import qualified Control.Monad as CM

streamGetnowMods :: Double -> Stream -> IO [Double]
streamGetnowMods mod s = do
  let mods = take 6 $ iterate (*2) mod
  result <- streamGetnow s
  return $! map (mod' result) mods

streamGetnowModsString :: Double -> Stream -> IO String
streamGetnowModsString mod s = do
  let mods = take 6 $ iterate (*2) mod
  results <- streamGetnowMods mod s
  cyclePos <- streamGetnow s
  let formattedResults = printf "c:%.0f |" (cyclePos+1) : zipWith (\x y -> printf "%d/%.0f" (floor x + 1) y) results mods
  return $ unwords formattedResults

printEverySecond :: Double -> Stream -> IO ()
printEverySecond mod s = CM.forever $ do
    result <- streamGetnowModsString mod s
    bpm <- getbpm s
    let bpmString = "t:" ++ printf "%.2f" bpm
    cps <- streamGetcps s
    let delay = floor (1 / cps * 1000000) -- convert cps to microseconds
    threadDelay delay
    putStrLn (bpmString ++ " | " ++ result)

startPrinting :: Double -> Stream -> IO (MVar ())
startPrinting mod s = do
    stopVar <- newEmptyMVar
    _ <- forkIO $ do
        let loop = do
                stopped <- tryTakeMVar stopVar
                CM.when (stopped == Nothing) $ do
                    printEverySecond mod s
                    loop
        loop
    return stopVar

stopPrinting :: MVar () -> IO ()
stopPrinting stopVar = do
    putMVar stopVar ()
    return ()

:}