dex :: Real b => b -> Pattern b -> Pattern c -> Pattern c
index sz indexpat pat =
  spread' (zoom' $ toRational sz) (toRational . (*(1-sz)) <$> indexpat) pat
  where
    zoom' tSz s = zoomArc (Arc s (s+tSz))

{-
-- | @prrw f rot (blen, vlen) beatPattern valuePattern@: pattern rotate/replace.
prrw :: (a -> b -> c) -> Int -> (Time, Time) -> Pattern a -> Pattern b -> Pattern c
prrw f rot (blen, vlen) beatPattern valuePattern =
  let
    ecompare (_,e1,_) (_,e2,_) = compare (fst e1) (fst e2)
    beats  = sortBy ecompare $ arc beatPattern (0, blen)
    values = fmap thd' . sortBy ecompare $ arc valuePattern (0, vlen)
    cycles = blen * (fromIntegral $ lcm (length beats) (length values) `div` (length beats))
  in
    _slow cycles $ stack $ zipWith
    (\( _, (start, end), v') v -> (start `rotR`) $ densityGap (1 / (end - start)) $ pure (f v' v))
    (sortBy ecompare $ arc (_fast cycles $ beatPattern) (0, blen))
    (drop (rot `mod` length values) $ cycle values)

-- | @prr rot (blen, vlen) beatPattern valuePattern@: pattern rotate/replace.
prr :: Int -> (Time, Time) -> Pattern String -> Pattern b -> Pattern b
prr = prrw $ flip const

{-|
@preplace (blen, plen) beats values@ combines the timing of @beats@ with the values
of @values@. Other ways of saying this are:
* sequential convolution
* @values@ quantized to @beats@.

Examples:

@
d1 $ sound $ preplace (1,1) "x [~ x] x x" "bd sn"
d1 $ sound $ preplace (1,1) "x(3,8)" "bd sn"
d1 $ sound $ "x(3,8)" <~> "bd sn"
d1 $ sound "[jvbass jvbass:5]*3" |+| (shape $ "1 1 1 1 1" <~> "0.2 0.9")
@

It is assumed the pattern fits into a single cycle. This works well with
pattern literals, but not always with patterns defined elsewhere. In those cases
use @preplace@ and provide desired pattern lengths:
@
let p = slow 2 $ "x x x"

d1 $ sound $ preplace (2,1) p "bd sn"
@
-}
preplace :: (Time, Time) -> Pattern String -> Pattern b -> Pattern b
preplace = preplaceWith $ flip const

-- | @prep@ is an alias for preplace.
prep :: (Time, Time) -> Pattern String -> Pattern b -> Pattern b
prep = preplace

preplace1 :: Pattern String -> Pattern b -> Pattern b
preplace1 = preplace (1, 1)

preplaceWith :: (a -> b -> c) -> (Time, Time) -> Pattern a -> Pattern b -> Pattern c
preplaceWith f (blen, plen) = prrw f 0 (blen, plen)

prw :: (a -> b -> c) -> (Time, Time) -> Pattern a -> Pattern b -> Pattern c
prw = preplaceWith

preplaceWith1 :: (a -> b -> c) -> Pattern a -> Pattern b -> Pattern c
preplaceWith1 f = prrw f 0 (1, 1)

prw1 :: (a -> b -> c) -> Pattern a -> Pattern b -> Pattern c
prw1 = preplaceWith1

(<~>) :: Pattern String -> Pattern b -> Pattern b
(<~>) = preplace (1, 1)

-- | @protate len rot p@ rotates pattern @p@ by @rot@ beats to the left.
-- @len@: length of the pattern, in cycles.
-- Example: @d1 $ every 4 (protate 2 (-1)) $ slow 2 $ sound "bd hh hh hh"@
protate :: Time -> Int -> Pattern a -> Pattern a
protate len rot p = prrw (flip const) rot (len, len) p p

prot :: Time -> Int -> Pattern a -> Pattern a
prot = protate

prot1 :: Int -> Pattern a -> Pattern a
prot1 = protate 1

{-| The @<<~@ operator rotates a unit pattern to the left, similar to @<~@,
but by events rather than linear time. The timing of the pattern remains constant:

@
d1 $ (1 <<~) $ sound "bd ~ sn hh"
-- will become
d1 $ sound "sn ~ hh bd"
@ -}

(<<~) :: Int -> Pattern a -> Pattern a
(<<~) = protate 1

-- | @~>>@ is like @<<~@ but for shifting to the right.
(~>>) :: Int -> Pattern a -> Pattern a
(~>>) = (<<~) . (0-)

-- | @pequal cycles p1 p2@: quickly test if @p1@ and @p2@ are the same.
pequal :: Ord a => Time -> Pattern a -> Pattern a -> Bool
pequal cycles p1 p2 = (sort $ arc p1 (0, cycles)) == (sort $ arc p2 (0, cycles))
-}

-- | @rot n p@ rotates the values in a pattern @p@ by @n@ beats to the left.
-- Example: @d1 $ every 4 (rot 2) $ slow 2 $ sound "bd hh hh hh"@
r
index :: Real b => b -> Pattern b -> Pattern c -> Pattern c
index sz indexpat pat =
  spread' (zoom' $ toRational sz) (toRational . (*(1-sz)) <$> indexpat) pat
  where
    zoom' tSz s = zoomArc (Arc s (s+tSz))

{-
-- | @prrw f rot (blen, vlen) beatPattern valuePattern@: pattern rotate/replace.
prrw :: (a -> b -> c) -> Int -> (Time, Time) -> Pattern a -> Pattern b -> Pattern c
prrw f rot (blen, vlen) beatPattern valuePattern =
  let
    ecompare (_,e1,_) (_,e2,_) = compare (fst e1) (fst e2)
    beats  = sortBy ecompare $ arc beatPattern (0, blen)
    values = fmap thd' . sortBy ecompare $ arc valuePattern (0, vlen)
    cycles = blen * (fromIntegral $ lcm (length beats) (length values) `div` (length beats))
  in
    _slow cycles $ stack $ zipWith
    (\( _, (start, end), v') v -> (start `rotR`) $ densityGap (1 / (end - start)) $ pure (f v' v))
    (sortBy ecompare $ arc (_fast cycles $ beatPattern) (0, blen))
    (drop (rot `mod` length values) $ cycle values)

-- | @prr rot (blen, vlen) beatPattern valuePattern@: pattern rotate/replace.
prr :: Int -> (Time, Time) -> Pattern String -> Pattern b -> Pattern b
prr = prrw $ flip const

{-|
@preplace (blen, plen) beats values@ combines the timing of @beats@ with the values
of @values@. Other ways of saying this are:
* sequential convolution
* @values@ quantized to @beats@.

Examples:

@
d1 $ sound $ preplace (1,1) "x [~ x] x x" "bd sn"
d1 $ sound $ preplace (1,1) "x(3,8)" "bd sn"
d1 $ sound $ "x(3,8)" <~> "bd sn"
d1 $ sound "[jvbass jvbass:5]*3" |+| (shape $ "1 1 1 1 1" <~> "0.2 0.9")
@

It is assumed the pattern fits into a single cycle. This works well with
pattern literals, but not always with patterns defined elsewhere. In those cases
use @preplace@ and provide desired pattern lengths:
@
let p = slow 2 $ "x x x"

d1 $ sound $ preplace (2,1) p "bd sn"
@
-}
preplace :: (Time, Time) -> Pattern String -> Pattern b -> Pattern b
preplace = preplaceWith $ flip const

-- | @prep@ is an alias for preplace.
prep :: (Time, Time) -> Pattern String -> Pattern b -> Pattern b
prep = preplace

preplace1 :: Pattern String -> Pattern b -> Pattern b
preplace1 = preplace (1, 1)

preplaceWith :: (a -> b -> c) -> (Time, Time) -> Pattern a -> Pattern b -> Pattern c
preplaceWith f (blen, plen) = prrw f 0 (blen, plen)

prw :: (a -> b -> c) -> (Time, Time) -> Pattern a -> Pattern b -> Pattern c
prw = preplaceWith

preplaceWith1 :: (a -> b -> c) -> Pattern a -> Pattern b -> Pattern c
preplaceWith1 f = prrw f 0 (1, 1)

prw1 :: (a -> b -> c) -> Pattern a -> Pattern b -> Pattern c
prw1 = preplaceWith1

(<~>) :: Pattern String -> Pattern b -> Pattern b
(<~>) = preplace (1, 1)

-- | @protate len rot p@ rotates pattern @p@ by @rot@ beats to the left.
-- @len@: length of the pattern, in cycles.
-- Example: @d1 $ every 4 (protate 2 (-1)) $ slow 2 $ sound "bd hh hh hh"@
protate :: Time -> Int -> Pattern a -> Pattern a
protate len rot p = prrw (flip const) rot (len, len) p p

prot :: Time -> Int -> Pattern a -> Pattern a
prot = protate

prot1 :: Int -> Pattern a -> Pattern a
prot1 = protate 1

{-| The @<<~@ operator rotates a unit pattern to the left, similar to @<~@,
but by events rather than linear time. The timing of the pattern remains constant:

@
d1 $ (1 <<~) $ sound "bd ~ sn hh"
-- will become
d1 $ sound "sn ~ hh bd"
@ -}

(<<~) :: Int -> Pattern a -> Pattern a
(<<~) = protate 1

-- | @~>>@ is like @<<~@ but for shifting to the right.
(~>>) :: Int -> Pattern a -> Pattern a
(~>>) = (<<~) . (0-)

-- | @pequal cycles p1 p2@: quickly test if @p1@ and @p2@ are the same.
pequal :: Ord a => Time -> Pattern a -> Pattern a -> Bool
pequal cycles p1 p2 = (sort $ arc p1 (0, cycles)) == (sort $ arc p2 (0, cycles))
-}

-- | @rot n p@ rotates the values in a pattern @p@ by @n@ beats to the left.
-- Example: @d1 $ every 4 (rot 2) $ slow 2 $ sound "bd hh hh hh"@
index sz indexpat pat =
  spread' (zoom' $ toRational sz) (toRational . (*(1-sz)) <$> indexpat) pat
  where
    zoom' tSz s = zoomArc (Arc s (s+tSz))

{-
-- | @prrw f rot (blen, vlen) beatPattern valuePattern@: pattern rotate/replace.
prrw :: (a -> b -> c) -> Int -> (Time, Time) -> Pattern a -> Pattern b -> Pattern c
prrw f rot (blen, vlen) beatPattern valuePattern =
  let
    ecompare (_,e1,_) (_,e2,_) = compare (fst e1) (fst e2)
    beats  = sortBy ecompare $ arc beatPattern (0, blen)
    values = fmap thd' . sortBy ecompare $ arc valuePattern (0, vlen)
    cycles = blen * (fromIntegral $ lcm (length beats) (length values) `div` (length beats))
  in
    _slow cycles $ stack $ zipWith
    (\( _, (start, end), v') v -> (start `rotR`) $ densityGap (1 / (end - start)) $ pure (f v' v))
    (sortBy ecompare $ arc (_fast cycles $ beatPattern) (0, blen))
    (drop (rot `mod` length values) $ cycle values)

-- | @prr rot (blen, vlen) beatPattern valuePattern@: pattern rotate/replace.
prr :: Int -> (Time, Time) -> Pattern String -> Pattern b -> Pattern b
prr = prrw $ flip const

{-|
@preplace (blen, plen) beats values@ combines the timing of @beats@ with the values
of @values@. Other ways of saying this are:
* sequential convolution
* @values@ quantized to @beats@.

Examples:

@
d1 $ sound $ preplace (1,1) "x [~ x] x x" "bd sn"
d1 $ sound $ preplace (1,1) "x(3,8)" "bd sn"
d1 $ sound $ "x(3,8)" <~> "bd sn"
d1 $ sound "[jvbass jvbass:5]*3" |+| (shape $ "1 1 1 1 1" <~> "0.2 0.9")
@

It is assumed the pattern fits into a single cycle. This works well with
pattern literals, but not always with patterns defined elsewhere. In those cases
use @preplace@ and provide desired pattern lengths:
@
let p = slow 2 $ "x x x"

d1 $ sound $ preplace (2,1) p "bd sn"
@
-}
preplace :: (Time, Time) -> Pattern String -> Pattern b -> Pattern b
preplace = preplaceWith $ flip const

-- | @prep@ is an alias for preplace.
prep :: (Time, Time) -> Pattern String -> Pattern b -> Pattern b
prep = preplace

preplace1 :: Pattern String -> Pattern b -> Pattern b
preplace1 = preplace (1, 1)

preplaceWith :: (a -> b -> c) -> (Time, Time) -> Pattern a -> Pattern b -> Pattern c
preplaceWith f (blen, plen) = prrw f 0 (blen, plen)

prw :: (a -> b -> c) -> (Time, Time) -> Pattern a -> Pattern b -> Pattern c
prw = preplaceWith

preplaceWith1 :: (a -> b -> c) -> Pattern a -> Pattern b -> Pattern c
preplaceWith1 f = prrw f 0 (1, 1)

prw1 :: (a -> b -> c) -> Pattern a -> Pattern b -> Pattern c
prw1 = preplaceWith1

(<~>) :: Pattern String -> Pattern b -> Pattern b
(<~>) = preplace (1, 1)

-- | @protate len rot p@ rotates pattern @p@ by @rot@ beats to the left.
-- @len@: length of the pattern, in cycles.
-- Example: @d1 $ every 4 (protate 2 (-1)) $ slow 2 $ sound "bd hh hh hh"@
protate :: Time -> Int -> Pattern a -> Pattern a
protate len rot p = prrw (flip const) rot (len, len) p p

prot :: Time -> Int -> Pattern a -> Pattern a
prot = protate

prot1 :: Int -> Pattern a -> Pattern a
prot1 = protate 1

{-| The @<<~@ operator rotates a unit pattern to the left, similar to @<~@,
but by events rather than linear time. The timing of the pattern remains constant:

@
d1 $ (1 <<~) $ sound "bd ~ sn hh"
-- will become
d1 $ sound "sn ~ hh bd"
@ -}

(<<~) :: Int -> Pattern a -> Pattern a
(<<~) = protate 1

-- | @~>>@ is like @<<~@ but for shifting to the right.
(~>>) :: Int -> Pattern a -> Pattern a
(~>>) = (<<~) . (0-)

-- | @pequal cycles p1 p2@: quickly test if @p1@ and @p2@ are the same.
pequal :: Ord a => Time -> Pattern a -> Pattern a -> Bool
pequal cycles p1 p2 = (sort $ arc p1 (0, cycles)) == (sort $ arc p2 (0, cycles))
-}

-- | @rot n p@ rotates the values in a pattern @p@ by @n@ beats to the left.
-- Example: @d1 $ every 4 (rot 2) $ slow 2 $ sound "bd hh hh hh"@