diff --git a/CHANGELOG.md b/CHANGELOG.md
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,17 +1,26 @@
-1.0.0.0
--------
-* initial release
-
-1.0.0.1
--------
-* removed the upper bounds of the dependencies
-
-1.1.0.0
--------
-* replaced the 'mpolynomials' dependency with 'hspray'
-* unit tests
-
-1.1.0.1
--------
-* unexported some useless functions
-* one more unit test
+1.0.0.0
+-------
+* initial release
+
+1.0.0.1
+-------
+* removed the upper bounds of the dependencies
+
+1.1.0.0
+-------
+* replaced the 'mpolynomials' dependency with 'hspray'
+* unit tests
+
+1.1.0.1
+-------
+* unexported some useless functions
+* one more unit test
+
+1.1.1.0
+-------
+* `schurPol` now returns a `Spray a`
+* added package upper bounds in the cabal file
+* increased the version of the dependencies **hspray** and **hypergeomatrix**
+* cleaned the code
+* tested with higher versions of GHC
+* new unit tests
diff --git a/LICENSE b/LICENSE
--- a/LICENSE
+++ b/LICENSE
@@ -1,674 +1,674 @@
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-GNU General Public License, you may choose any version ever published
-by the Free Software Foundation.
-
-  If the Program specifies that a proxy can decide which future
-versions of the GNU General Public License can be used, that proxy's
-public statement of acceptance of a version permanently authorizes you
-to choose that version for the Program.
-
-  Later license versions may give you additional or different
-permissions.  However, no additional obligations are imposed on any
-author or copyright holder as a result of your choosing to follow a
-later version.
-
-  15. Disclaimer of Warranty.
-
-  THERE IS NO WARRANTY FOR THE PROGRAM, TO THE EXTENT PERMITTED BY
-APPLICABLE LAW.  EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT
-HOLDERS AND/OR OTHER PARTIES PROVIDE THE PROGRAM "AS IS" WITHOUT WARRANTY
-OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO,
-THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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-IS WITH YOU.  SHOULD THE PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF
-ALL NECESSARY SERVICING, REPAIR OR CORRECTION.
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-  16. Limitation of Liability.
-
-  IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING
-WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MODIFIES AND/OR CONVEYS
-THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES, INCLUDING ANY
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-USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED TO LOSS OF
-DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD
-PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER PROGRAMS),
-EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF
-SUCH DAMAGES.
-
-  17. Interpretation of Sections 15 and 16.
-
-  If the disclaimer of warranty and limitation of liability provided
-above cannot be given local legal effect according to their terms,
-reviewing courts shall apply local law that most closely approximates
-an absolute waiver of all civil liability in connection with the
-Program, unless a warranty or assumption of liability accompanies a
-copy of the Program in return for a fee.
-
-                     END OF TERMS AND CONDITIONS
-
-            How to Apply These Terms to Your New Programs
-
-  If you develop a new program, and you want it to be of the greatest
-possible use to the public, the best way to achieve this is to make it
-free software which everyone can redistribute and change under these terms.
-
-  To do so, attach the following notices to the program.  It is safest
-to attach them to the start of each source file to most effectively
-state the exclusion of warranty; and each file should have at least
-the "copyright" line and a pointer to where the full notice is found.
-
-    <one line to give the program's name and a brief idea of what it does.>
-    Copyright (C) <year>  <name of author>
-
-    This program is free software: you can redistribute it and/or modify
-    it under the terms of the GNU General Public License as published by
-    the Free Software Foundation, either version 3 of the License, or
-    (at your option) any later version.
-
-    This program is distributed in the hope that it will be useful,
-    but WITHOUT ANY WARRANTY; without even the implied warranty of
-    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-    GNU General Public License for more details.
-
-    You should have received a copy of the GNU General Public License
-    along with this program.  If not, see <https://www.gnu.org/licenses/>.
-
-Also add information on how to contact you by electronic and paper mail.
-
-  If the program does terminal interaction, make it output a short
-notice like this when it starts in an interactive mode:
-
-    <program>  Copyright (C) <year>  <name of author>
-    This program comes with ABSOLUTELY NO WARRANTY; for details type `show w'.
-    This is free software, and you are welcome to redistribute it
-    under certain conditions; type `show c' for details.
-
-The hypothetical commands `show w' and `show c' should show the appropriate
-parts of the General Public License.  Of course, your program's commands
-might be different; for a GUI interface, you would use an "about box".
-
-  You should also get your employer (if you work as a programmer) or school,
-if any, to sign a "copyright disclaimer" for the program, if necessary.
-For more information on this, and how to apply and follow the GNU GPL, see
-<https://www.gnu.org/licenses/>.
-
-  The GNU General Public License does not permit incorporating your program
-into proprietary programs.  If your program is a subroutine library, you
-may consider it more useful to permit linking proprietary applications with
-the library.  If this is what you want to do, use the GNU Lesser General
-Public License instead of this License.  But first, please read
-<https://www.gnu.org/licenses/why-not-lgpl.html>.
+                    GNU GENERAL PUBLIC LICENSE
+                       Version 3, 29 June 2007
+
+ Copyright (C) 2007 Free Software Foundation, Inc. <https://fsf.org/>
+ Everyone is permitted to copy and distribute verbatim copies
+ of this license document, but changing it is not allowed.
+
+                            Preamble
+
+  The GNU General Public License is a free, copyleft license for
+software and other kinds of works.
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+  The licenses for most software and other practical works are designed
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+  Developers that use the GNU GPL protect your rights with two steps:
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+  Some devices are designed to deny users access to install or run
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+
+                       TERMS AND CONDITIONS
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+to attach them to the start of each source file to most effectively
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+    Copyright (C) <year>  <name of author>
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+    it under the terms of the GNU General Public License as published by
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+
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+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
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+    along with this program.  If not, see <https://www.gnu.org/licenses/>.
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+if any, to sign a "copyright disclaimer" for the program, if necessary.
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+<https://www.gnu.org/licenses/>.
+
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+into proprietary programs.  If your program is a subroutine library, you
+may consider it more useful to permit linking proprietary applications with
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+Public License instead of this License.  But first, please read
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diff --git a/README.md b/README.md
--- a/README.md
+++ b/README.md
@@ -1,35 +1,42 @@
-# jackpolynomials
-
-Schur polynomials have applications in combinatorics and zonal polynomials have
-applications in multivariate statistics. They are particular cases of
-[Jack polynomials](https://en.wikipedia.org/wiki/Jack_function). This package
-allows to evaluate these polynomials. It can also compute their symbolic form.
-
-___
-
-```haskell
-import Math.Algebra.Jack
-import Data.Ratio
-jack [1, 1] [3, 1] (2%1)
--- 48 % 1
-```
-
-```haskell
-import Math.Algebra.JackPol
-import Data.Ratio
-import Math.Algebra.Spray
-jp = jackPol 2 [3, 1] (2%1)
-prettySpray show "x" jp
--- "(18 % 1) * x^(1, 3) + (12 % 1) * x^(2, 2) + (18 % 1) * x^(3, 1)"
-evalSpray jp [1, 1]
--- 48 % 1
-```
-
-
-## References
-
-* I.G. Macdonald. *Symmetric Functions and Hall Polynomials*. Oxford Mathematical Monographs. The Clarendon Press Oxford University Press, New York, second edition, 1995.
-
-* J. Demmel and P. Koev. *Accurate and efficient evaluation of Schur and Jack functions*. Mathematics of computations, vol. 75, n. 253, 223-229, 2005.
-
-* Jack polynomials. <https://www.symmetricfunctions.com/jack.htm>.
+# jackpolynomials
+
+*Jack, zonal, and Schur polynomials.*
+
+<!-- badges: start -->
+[![Stack-lts](https://github.com/stla/jackpolynomials/actions/workflows/Stack-lts.yml/badge.svg)](https://github.com/stla/jackpolynomials/actions/workflows/Stack-lts.yml)
+[![Stack-nightly](https://github.com/stla/jackpolynomials/actions/workflows/Stack-nightly.yml/badge.svg)](https://github.com/stla/jackpolynomials/actions/workflows/Stack-nightly.yml)
+<!-- badges: end -->
+
+Schur polynomials have applications in combinatorics and zonal polynomials have
+applications in multivariate statistics. They are particular cases of
+[Jack polynomials](https://en.wikipedia.org/wiki/Jack_function). This package
+allows to evaluate these polynomials. It can also compute their symbolic form.
+
+___
+
+```haskell
+import Math.Algebra.Jack
+import Data.Ratio
+jack [1, 1] [3, 1] (2%1)
+-- 48 % 1
+```
+
+```haskell
+import Math.Algebra.JackPol
+import Data.Ratio
+import Math.Algebra.Hspray
+jp = jackPol 2 [3, 1] (2%1)
+putStrLn $ prettySpray' jp
+-- (18 % 1) x1^3x2 + (12 % 1) x1^2x2^2 + (18 % 1) x1x2^3
+evalSpray jp [1, 1]
+-- 48 % 1
+```
+
+
+## References
+
+* I.G. Macdonald. *Symmetric Functions and Hall Polynomials*. Oxford Mathematical Monographs. The Clarendon Press Oxford University Press, New York, second edition, 1995.
+
+* J. Demmel and P. Koev. *Accurate and efficient evaluation of Schur and Jack functions*. Mathematics of computations, vol. 75, n. 253, 223-229, 2005.
+
+* Jack polynomials. <https://www.symmetricfunctions.com/jack.htm>.
diff --git a/Setup.hs b/Setup.hs
--- a/Setup.hs
+++ b/Setup.hs
@@ -1,2 +1,2 @@
-import Distribution.Simple
-main = defaultMain
+import Distribution.Simple
+main = defaultMain
diff --git a/jackpolynomials.cabal b/jackpolynomials.cabal
--- a/jackpolynomials.cabal
+++ b/jackpolynomials.cabal
@@ -1,47 +1,57 @@
-name:                jackpolynomials
-version:             1.1.0.1
-synopsis:            Jack, zonal, and Schur polynomials
-description:         This library can evaluate Jack polynomials, zonal polynomials and Schur polynomials. It is also able to compute them in symbolic form.
-homepage:            https://github.com/stla/jackpolynomials#readme
-license:             GPL-3
-license-file:        LICENSE
-author:              Stéphane Laurent
-maintainer:          laurent_step@outlook.fr
-copyright:           2022 Stéphane Laurent
-category:            Math, Algebra
-build-type:          Simple
-extra-source-files:  README.md
-                     CHANGELOG.md
-cabal-version:       >=1.10
-
-library
-  hs-source-dirs:      src
-  exposed-modules:     Math.Algebra.Jack.HypergeoPQ
-                     , Math.Algebra.Jack
-                     , Math.Algebra.JackPol
-  other-modules:       Math.Algebra.Jack.Internal
-  build-depends:       base >= 4.7 && < 5
-                     , ilist >= 0.4.0.1
-                     , array >= 0.5.4.0
-                     , lens >= 5.0.1
-                     , math-functions >= 0.3.4.2
-                     , hspray >= 0.1.0.0
-                     , numeric-prelude >= 0.4.4
-  default-language:    Haskell2010
-  ghc-options:         -Wall
-
-test-suite unit-tests
-  type:                 exitcode-stdio-1.0
-  main-is:              Main.hs
-  hs-source-dirs:       tests/
-  Build-Depends:        base >= 4.7 && < 5
-                      , tasty
-                      , tasty-hunit
-                      , jackpolynomials
-                      , hspray
-                      , hypergeomatrix
-  Default-Language:     Haskell2010
-
-source-repository head
-  type:     git
-  location: https://github.com/stla/jackpolynomials
+name:                jackpolynomials
+version:             1.1.1.0
+synopsis:            Jack, zonal, and Schur polynomials
+description:         This library can evaluate Jack polynomials, zonal polynomials and Schur polynomials. It is also able to compute them in symbolic form.
+homepage:            https://github.com/stla/jackpolynomials#readme
+license:             GPL-3
+license-file:        LICENSE
+author:              Stéphane Laurent
+maintainer:          laurent_step@outlook.fr
+copyright:           2022 Stéphane Laurent
+category:            Math, Algebra
+build-type:          Simple
+extra-source-files:  README.md
+                     CHANGELOG.md
+cabal-version:       >=1.10
+
+library
+  hs-source-dirs:      src
+  exposed-modules:     Math.Algebra.Jack.HypergeoPQ
+                     , Math.Algebra.Jack
+                     , Math.Algebra.JackPol
+  other-modules:       Math.Algebra.Jack.Internal
+  build-depends:       base >= 4.7 && < 5
+                     , ilist >= 0.4.0.1 && < 0.4.1
+                     , array >= 0.5.4.0 && < 0.6
+                     , lens >= 5.0.1 && < 5.3
+                     , math-functions >= 0.3.4.2 && < 0.3.5
+                     , hspray >= 0.2.2.0 && < 1
+                     , numeric-prelude >= 0.4.4 && < 0.5
+  other-extensions:    ScopedTypeVariables
+                     , BangPatterns
+  default-language:    Haskell2010
+  ghc-options:         -Wall
+                       -Wcompat
+                       -Widentities
+                       -Wincomplete-record-updates
+                       -Wincomplete-uni-patterns
+                       -Wmissing-export-lists
+                       -Wmissing-home-modules
+                       -Wpartial-fields
+                       -Wredundant-constraints
+
+test-suite unit-tests
+  type:                 exitcode-stdio-1.0
+  main-is:              Main.hs
+  hs-source-dirs:       tests/
+  Build-Depends:        base >= 4.7 && < 5
+                      , tasty >= 1.4 && < 1.6
+                      , tasty-hunit >= 0.10 && < 0.11
+                      , jackpolynomials
+                      , hspray >= 0.2.2.0 && < 1
+                      , hypergeomatrix >= 1.1.0.2 && < 2
+  Default-Language:     Haskell2010
+
+source-repository head
+  type:     git
+  location: https://github.com/stla/jackpolynomials
diff --git a/src/Math/Algebra/Jack.hs b/src/Math/Algebra/Jack.hs
--- a/src/Math/Algebra/Jack.hs
+++ b/src/Math/Algebra/Jack.hs
@@ -1,121 +1,136 @@
-{-# LANGUAGE BangPatterns        #-}
-{-# LANGUAGE ScopedTypeVariables #-}
-module Math.Algebra.Jack
-  (schur, jack, zonal)
-  where
-import Control.Lens               ( (.~), element )
-import Data.Array                 ( Array, (!), (//), listArray )
-import Data.Maybe                 ( fromJust, isJust )
-import Math.Algebra.Jack.Internal ( _N, hookLengths, _betaratio, _isPartition, Partition )
-import Numeric.SpecFunctions      ( factorial )
-
--- | Evaluation of Jack polynomial
-jack :: forall a. (Fractional a, Ord a) 
-  => [a] -- ^ values of the variables
-  -> Partition -- ^ partition of integers
-  -> a -- ^ alpha parameter
-  -> a
-jack x lambda alpha =
-  case _isPartition lambda && alpha > 0 of
-    False -> if _isPartition lambda
-      then error "alpha must be strictly positive"
-      else error "lambda is not a valid integer partition"
-    True -> jac (length x) 0 lambda lambda arr0 1
-      where
-      nll = _N lambda lambda
-      n = length x
-      arr0 = listArray ((1, 1), (nll, n)) (replicate (nll * n) Nothing)
-      theproduct :: Int -> a
-      theproduct nu0 = if nu0 <= 1
-        then 1
-        else product $ map (\i -> alpha * fromIntegral i + 1) [1 .. nu0-1]
-      jac :: Int -> Int -> [Int] -> [Int] -> Array (Int,Int) (Maybe a) -> a -> a
-      jac m k mu nu arr beta
-        | null nu || head nu == 0 || m == 0 = 1
-        | length nu > m && nu!!m > 0 = 0
-        | m == 1 = head x ^ head nu * theproduct (head nu)
-        | k == 0 && isJust (arr ! (_N lambda nu, m)) =
-                      fromJust $ arr ! (_N lambda nu, m)
-        | otherwise = s
-          where
-            s = go (jac (m-1) 0 nu nu arr 1 * beta * x!!(m-1) ^ (sum mu - sum nu))
-                (max 1 k)
-            go :: a -> Int -> a
-            go !ss ii
-              | length nu < ii || nu!!(ii-1) == 0 = ss
-              | otherwise =
-                let u = nu!!(ii-1) in
-                if length nu == ii && u > 0 || u > nu!!ii
-                  then
-                    let nu' = (element (ii-1) .~ u-1) nu in
-                    let gamma = beta * _betaratio mu nu ii alpha in
-                    if u > 1
-                      then
-                        go (ss + jac m ii mu nu' arr gamma) (ii + 1)
-                      else
-                        if head nu' == 0
-                          then
-                            go (ss + gamma * x!!(m-1)^ sum mu) (ii + 1)
-                          else
-                            let arr' = arr // [((_N lambda nu, m), Just ss)] in
-                            let jck = jac (m-1) 0 nu' nu' arr' 1 in
-                            let jck' = jck * gamma *
-                                        x!!(m-1) ^ (sum mu - sum nu') in
-                            go (ss+jck') (ii+1)
-                  else
-                    go ss (ii+1)
-
--- | Evaluation of zonal polynomial
-zonal :: (Fractional a, Ord a) 
-  => [a] -- ^ values of the variables
-  -> Partition -- ^ partition of integers
-  -> a
-zonal x lambda = c * jck
-  where
-    k = sum lambda
-    jlambda = product (hookLengths lambda 2)
-    c = 2^k * realToFrac (factorial k) / jlambda
-    jck = jack x lambda 2
-
--- | Evaluation of Schur polynomial
-schur :: forall a. Fractional a 
-  => [a] -- ^ values of the variables
-  -> Partition -- ^ partition of integers 
-  -> a
-schur x lambda =
-  case _isPartition lambda of
-    False -> error "lambda is not a valid integer partition"
-    True -> sch n 1 lambda arr0
-      where
-        nll = _N lambda lambda
-        n = length x
-        arr0 = listArray ((1, 1), (nll, n)) (replicate (nll * n) Nothing)
-        sch :: Int -> Int -> [Int] -> Array (Int,Int) (Maybe a) -> a
-        sch m k nu arr
-          | null nu || head nu == 0 || m == 0 = 1
-          | length nu > m && nu!!m > 0 = 0
-          | m == 1 = head x ^ head nu
-          | isJust (arr ! (_N lambda nu, m)) = fromJust $ arr ! (_N lambda nu, m)
-          | otherwise = s
-            where
-              s = go (sch (m-1) 1 nu arr) k
-              go :: Fractional a => a -> Int -> a
-              go !ss ii
-                | length nu < ii || nu!!(ii-1) == 0 = ss
-                | otherwise =
-                  let u = nu!!(ii-1) in
-                  if length nu == ii && u > 0 || u > nu !! ii
-                    then
-                      let nu' = (element (ii-1) .~ u-1) nu in
-                      if u > 1
-                        then
-                          go (ss + x!!(m-1) * sch m ii nu' arr) (ii + 1)
-                        else
-                          if head nu' == 0
-                            then
-                              go (ss + x!!(m-1)) (ii + 1)
-                            else
-                              let arr' = arr // [((_N lambda nu, m), Just ss)] in
-                              go (ss + x!!(m-1) * sch (m-1) 1 nu' arr') (ii + 1)
-                    else
-                      go ss (ii+1)
+{-|
+Module      : Math.Algebra.JackPol
+Description : Evaluation of Jack polynomials.
+Copyright   : (c) Stéphane Laurent, 2024
+License     : GPL-3
+Maintainer  : laurent_step@outlook.fr
+
+Evaluation of Jack polynomials, zonal polynomials, and Schur polynomials. 
+See README for examples and references.
+-}
+
+{-# LANGUAGE BangPatterns        #-}
+{-# LANGUAGE ScopedTypeVariables #-}
+module Math.Algebra.Jack
+  (jack, zonal, schur)
+  where
+import qualified Algebra.Additive as AA
+import qualified Algebra.Ring     as AR
+import Control.Lens               ( (.~), element )
+import Data.Array                 ( Array, (!), (//), listArray )
+import Data.Maybe                 ( fromJust, isJust )
+import Math.Algebra.Jack.Internal ( _N, hookLengths, _betaratio, _isPartition, Partition )
+import Numeric.SpecFunctions      ( factorial )
+
+-- | Evaluation of Jack polynomial
+jack :: forall a. (Fractional a, Ord a) 
+  => [a]       -- ^ values of the variables
+  -> Partition -- ^ partition of integers
+  -> a         -- ^ alpha parameter
+  -> a
+jack []       _      _     = error "jack: empty list of variables"
+jack x@(x0:_) lambda alpha =
+  case _isPartition lambda && alpha > 0 of
+    False -> if _isPartition lambda
+      then error "jack: alpha must be strictly positive"
+      else error "jack: invalid integer partition"
+    True -> jac (length x) 0 lambda lambda arr0 1
+      where
+      nll = _N lambda lambda
+      n = length x
+      arr0 = listArray ((1, 1), (nll, n)) (replicate (nll * n) Nothing)
+      theproduct :: Int -> a
+      theproduct nu0 = if nu0 <= 1
+        then 1
+        else product $ map (\i -> alpha * fromIntegral i + 1) [1 .. nu0-1]
+      jac :: Int -> Int -> [Int] -> [Int] -> Array (Int,Int) (Maybe a) -> a -> a
+      jac m k mu nu arr beta
+        | null nu || nu!!0 == 0 || m == 0 = 1
+        | length nu > m && nu!!m > 0 = 0
+        | m == 1 = x0 ^ (nu!!0) * theproduct (nu!!0)
+        | k == 0 && isJust (arr ! (_N lambda nu, m)) =
+                      fromJust $ arr ! (_N lambda nu, m)
+        | otherwise = s
+          where
+            s = go (jac (m-1) 0 nu nu arr 1 * beta * x!!(m-1) ^ (sum mu - sum nu))
+                (max 1 k)
+            go :: a -> Int -> a
+            go !ss ii
+              | length nu < ii || nu!!(ii-1) == 0 = ss
+              | otherwise =
+                let u = nu!!(ii-1) in
+                if length nu == ii && u > 0 || u > nu!!ii
+                  then
+                    let nu' = (element (ii-1) .~ u-1) nu in
+                    let gamma = beta * _betaratio mu nu ii alpha in
+                    if u > 1
+                      then
+                        go (ss + jac m ii mu nu' arr gamma) (ii + 1)
+                      else
+                        if nu' !! 0 == 0
+                          then
+                            go (ss + gamma * x!!(m-1)^ sum mu) (ii + 1)
+                          else
+                            let arr' = arr // [((_N lambda nu, m), Just ss)] in
+                            let jck = jac (m-1) 0 nu' nu' arr' 1 in
+                            let jck' = jck * gamma *
+                                        x!!(m-1) ^ (sum mu - sum nu') in
+                            go (ss+jck') (ii+1)
+                  else
+                    go ss (ii+1)
+
+-- | Evaluation of zonal polynomial
+zonal :: (Fractional a, Ord a) 
+  => [a]       -- ^ values of the variables
+  -> Partition -- ^ partition of integers
+  -> a
+zonal x lambda = c * jck
+  where
+    k = sum lambda
+    jlambda = product (hookLengths lambda 2)
+    c = 2^k * realToFrac (factorial k) / jlambda
+    jck = jack x lambda 2
+
+-- | Evaluation of Schur polynomial
+schur :: forall a. AR.C a 
+  => [a]       -- ^ values of the variables
+  -> Partition -- ^ partition of integers 
+  -> a
+schur []       _      = error "schur: empty list of variables"
+schur x@(x0:_) lambda =
+  case _isPartition lambda of
+    False -> error "schur: invalid integer partition"
+    True -> sch n 1 lambda arr0
+      where
+        nll = _N lambda lambda
+        n = length x
+        arr0 = listArray ((1, 1), (nll, n)) (replicate (nll * n) Nothing)
+        sch :: Int -> Int -> [Int] -> Array (Int,Int) (Maybe a) -> a
+        sch m k nu arr
+          | null nu || nu!!0 == 0 || m == 0 = AR.one
+          | length nu > m && nu!!m > 0 = AA.zero
+          | m == 1 = AR.product (replicate (nu!!0) x0)
+          | isJust (arr ! (_N lambda nu, m)) = fromJust $ arr ! (_N lambda nu, m)
+          | otherwise = s
+            where
+              s = go (sch (m-1) 1 nu arr) k
+              go :: a -> Int -> a
+              go !ss ii
+                | length nu < ii || nu!!(ii-1) == 0 = ss
+                | otherwise =
+                  let u = nu!!(ii-1) in
+                  if length nu == ii && u > 0 || u > nu !! ii
+                    then
+                      let nu' = (element (ii-1) .~ u-1) nu in
+                      if u > 1
+                        then
+                          go (ss AA.+ x!!(m-1) AR.* sch m ii nu' arr) (ii + 1)
+                        else
+                          if nu' !! 0 == 0
+                            then
+                              go (ss AA.+ x!!(m-1)) (ii + 1)
+                            else
+                              let arr' = arr // [((_N lambda nu, m), Just ss)] in
+                              go (ss AA.+ x!!(m-1) AR.* sch (m-1) 1 nu' arr') (ii + 1)
+                    else
+                      go ss (ii+1)
diff --git a/src/Math/Algebra/Jack/HypergeoPQ.hs b/src/Math/Algebra/Jack/HypergeoPQ.hs
--- a/src/Math/Algebra/Jack/HypergeoPQ.hs
+++ b/src/Math/Algebra/Jack/HypergeoPQ.hs
@@ -1,33 +1,33 @@
-module Math.Algebra.Jack.HypergeoPQ
-  ( hypergeoPQ, _allPartitions
-  ) where
-import           Math.Algebra.Jack              ( zonal )
-
-gpochhammer :: Fractional a => a -> [Int] -> a -> a
-gpochhammer a kappa alpha = product $ map
-  (\i -> product $ map
-    (\j -> a - (fromIntegral i - 1) / alpha + fromIntegral j - 1)
-    [1 .. kappa !! (i - 1)]
-  )
-  [1 .. length kappa]
-
-hcoeff :: Fractional a => [a] -> [a] -> [Int] -> a -> a
-hcoeff a b kappa alpha = numerator / denominator / 
-  fromIntegral (factorial (sum kappa))
- where
-  factorial n = product [1 .. n]
-  numerator   = product $ map (\x -> gpochhammer x kappa alpha) a
-  denominator = product $ map (\x -> gpochhammer x kappa alpha) b
-
-_allPartitions :: Int -> [[Int]]
-_allPartitions m = [[]] ++ (map reverse (concat ps))
- where
-  ps      = [] : map parts [1 .. m]
-  parts n = [n] : [ x : p | x <- [1 .. n], p <- ps !! (n - x), x <= head p ]
-
--- | Inefficient hypergeometric function of a matrix argument
-hypergeoPQ :: (Fractional a, Ord a) => Int -> [a] -> [a] -> [a] -> a
-hypergeoPQ m a b x = sum $ map (\kappa -> coeff kappa * zonal x kappa) kappas
- where
-  kappas      = filter (\kap -> length kap <= length x) (_allPartitions m)
-  coeff kappa = hcoeff a b kappa 2
+module Math.Algebra.Jack.HypergeoPQ
+  ( hypergeoPQ
+  ) where
+import           Math.Algebra.Jack              ( zonal )
+
+gpochhammer :: Fractional a => a -> [Int] -> a -> a
+gpochhammer a kappa alpha = product $ map
+  (\i -> product $ map
+    (\j -> a - (fromIntegral i - 1) / alpha + fromIntegral j - 1)
+    [1 .. kappa !! (i - 1)]
+  )
+  [1 .. length kappa]
+
+hcoeff :: Fractional a => [a] -> [a] -> [Int] -> a -> a
+hcoeff a b kappa alpha = numerator / denominator / 
+  fromIntegral (factorial (sum kappa))
+ where
+  factorial n = product [1 .. n]
+  numerator   = product $ map (\x -> gpochhammer x kappa alpha) a
+  denominator = product $ map (\x -> gpochhammer x kappa alpha) b
+
+_allPartitions :: Int -> [[Int]]
+_allPartitions m = [] : map reverse (concat ps)
+ where
+  ps      = [] : map parts [1 .. m]
+  parts n = [n] : [ x : p | x <- [1 .. n], p <- ps !! (n - x), x <= p!!0 ]
+
+-- | Inefficient hypergeometric function of a matrix argument (for testing purpose)
+hypergeoPQ :: (Fractional a, Ord a) => Int -> [a] -> [a] -> [a] -> a
+hypergeoPQ m a b x = sum $ map (\kappa -> coeff kappa * zonal x kappa) kappas
+ where
+  kappas      = filter (\kap -> length kap <= length x) (_allPartitions m)
+  coeff kappa = hcoeff a b kappa 2
diff --git a/src/Math/Algebra/Jack/Internal.hs b/src/Math/Algebra/Jack/Internal.hs
--- a/src/Math/Algebra/Jack/Internal.hs
+++ b/src/Math/Algebra/Jack/Internal.hs
@@ -1,77 +1,71 @@
-{-# LANGUAGE BangPatterns #-}
-module Math.Algebra.Jack.Internal
-  where
-import qualified Algebra.Ring    as AR
-import           Data.List.Index ( iconcatMap )
-
-type Partition = [Int]
-
-_isPartition :: Partition -> Bool
-_isPartition []  = True
-_isPartition [x] = x > 0
-_isPartition (x:xs@(y:_)) = (x >= y) && _isPartition xs
-
-_diffSequence :: [Int] -> [Int]
-_diffSequence = go where
-  go (x:ys@(y:_)) = (x-y) : go ys 
-  go [x] = [x]
-  go []  = []
-
-_dualPartition :: Partition -> Partition
-_dualPartition [] = []
-_dualPartition xs = go 0 (_diffSequence xs) [] where
-  go !i (d:ds) acc = go (i+1) ds (d:acc)
-  go n  []     acc = finish n acc 
-  finish !j (k:ks) = replicate k j ++ finish (j-1) ks
-  finish _  []     = []
-
-_ij :: Partition -> ([Int], [Int])
-_ij lambda =
-  (
-    iconcatMap (\i a ->  replicate a (i + 1)) lambda,
-    concatMap (\a -> [1 .. a]) (filter (>0) lambda)
-  )
-
-_convParts :: Num b => [Int] -> ([b], [b])
-_convParts lambda =
-  (map fromIntegral lambda, map fromIntegral (_dualPartition lambda))
-
-_N :: [Int] -> [Int] -> Int
-_N lambda mu = sum $ zipWith (*) mu prods
-  where
-  prods = map (\i -> product $ drop i (map (+1) lambda)) [1 .. length lambda]
-
-hookLengths :: Fractional a => Partition -> a -> [a]
-hookLengths lambda alpha = upper ++ lower
-  where
-    (i, j) = _ij lambda
-    (lambda', lambdaConj') = _convParts lambda
-    upper = zipWith (fup lambdaConj' lambda') i j
-      where
-        fup x y ii jj =
-          x!!(jj-1) - fromIntegral ii + alpha * (y!!(ii-1) - fromIntegral jj + 1)
-    lower = zipWith (flow lambdaConj' lambda') i j
-      where
-        flow x y ii jj =
-          x!!(jj-1) - fromIntegral ii + 1 + alpha * (y!!(ii-1) - fromIntegral jj)
-
-hookLengths' :: (Fractional a, AR.C a) => Partition -> a -> [a]
-hookLengths' = hookLengths
-
-_betaratio :: Fractional a => Partition -> Partition -> Int -> a -> a
-_betaratio kappa mu k alpha = alpha * prod1 * prod2 * prod3
-  where
-    mukm1 = mu !! (k-1)
-    t = fromIntegral k - alpha * fromIntegral mukm1
-    u = zipWith (\s kap -> t + 1 - fromIntegral s + alpha * fromIntegral kap)
-                [1 .. k] kappa 
-    v = zipWith (\s m -> t - fromIntegral s + alpha * fromIntegral m)
-                [1 .. k-1] mu 
-    w = zipWith (\s m -> fromIntegral m - t - alpha * fromIntegral s)
-                [1 .. mukm1-1] (_dualPartition mu)
-    prod1 = product $ map (\x -> x / (x + alpha - 1)) u
-    prod2 = product $ map (\x -> (x + alpha) / x) v
-    prod3 = product $ map (\x -> (x + alpha) / x) w
-
-_betaratio' :: (Fractional a, AR.C a) => [Int] -> [Int] -> Int -> a -> a
-_betaratio' = _betaratio
+{-# LANGUAGE BangPatterns #-}
+module Math.Algebra.Jack.Internal
+  (Partition, hookLengths, _betaratio, _isPartition, _N)
+  where
+import           Data.List.Index ( iconcatMap )
+
+type Partition = [Int]
+
+_isPartition :: Partition -> Bool
+_isPartition []  = True
+_isPartition [x] = x > 0
+_isPartition (x:xs@(y:_)) = (x >= y) && _isPartition xs
+
+_diffSequence :: [Int] -> [Int]
+_diffSequence = go where
+  go (x:ys@(y:_)) = (x-y) : go ys 
+  go [x] = [x]
+  go []  = []
+
+_dualPartition :: Partition -> Partition
+_dualPartition [] = []
+_dualPartition xs = go 0 (_diffSequence xs) [] where
+  go !i (d:ds) acc = go (i+1) ds (d:acc)
+  go n  []     acc = finish n acc 
+  finish !j (k:ks) = replicate k j ++ finish (j-1) ks
+  finish _  []     = []
+
+_ij :: Partition -> ([Int], [Int])
+_ij lambda =
+  (
+    iconcatMap (\i a ->  replicate a (i + 1)) lambda,
+    concatMap (\a -> [1 .. a]) (filter (>0) lambda)
+  )
+
+_convParts :: Num b => [Int] -> ([b], [b])
+_convParts lambda =
+  (map fromIntegral lambda, map fromIntegral (_dualPartition lambda))
+
+_N :: [Int] -> [Int] -> Int
+_N lambda mu = sum $ zipWith (*) mu prods
+  where
+  prods = map (\i -> product $ drop i (map (+1) lambda)) [1 .. length lambda]
+
+hookLengths :: Fractional a => Partition -> a -> [a]
+hookLengths lambda alpha = upper ++ lower
+  where
+    (i, j) = _ij lambda
+    (lambda', lambdaConj') = _convParts lambda
+    upper = zipWith (fup lambdaConj' lambda') i j
+      where
+        fup x y ii jj =
+          x!!(jj-1) - fromIntegral ii + alpha * (y!!(ii-1) - fromIntegral jj + 1)
+    lower = zipWith (flow lambdaConj' lambda') i j
+      where
+        flow x y ii jj =
+          x!!(jj-1) - fromIntegral ii + 1 + alpha * (y!!(ii-1) - fromIntegral jj)
+
+_betaratio :: Fractional a => Partition -> Partition -> Int -> a -> a
+_betaratio kappa mu k alpha = alpha * prod1 * prod2 * prod3
+  where
+    mukm1 = mu !! (k-1)
+    t = fromIntegral k - alpha * fromIntegral mukm1
+    u = zipWith (\s kap -> t + 1 - fromIntegral s + alpha * fromIntegral kap)
+                [1 .. k] kappa 
+    v = zipWith (\s m -> t - fromIntegral s + alpha * fromIntegral m)
+                [1 .. k-1] mu 
+    w = zipWith (\s m -> fromIntegral m - t - alpha * fromIntegral s)
+                [1 .. mukm1-1] (_dualPartition mu)
+    prod1 = product $ map (\x -> x / (x + alpha - 1)) u
+    prod2 = product $ map (\x -> (x + alpha) / x) v
+    prod3 = product $ map (\x -> (x + alpha) / x) w
diff --git a/src/Math/Algebra/JackPol.hs b/src/Math/Algebra/JackPol.hs
--- a/src/Math/Algebra/JackPol.hs
+++ b/src/Math/Algebra/JackPol.hs
@@ -1,125 +1,137 @@
-{-# LANGUAGE BangPatterns        #-}
-{-# LANGUAGE ScopedTypeVariables #-}
-module Math.Algebra.JackPol
-  (schurPol, jackPol, zonalPol)
-  where
-import qualified Algebra.Ring as AR
-import           Control.Lens               ( (.~), element )
-import           Data.Array                 ( Array, (!), (//), listArray )
-import           Data.Maybe                 ( fromJust, isJust )
-import           Math.Algebra.Jack.Internal ( _betaratio', hookLengths, _N
-                                            , _isPartition, Partition )
-import           Math.Algebra.Hspray        ( (*^), (^**^), (^*^), (^+^)
-                                            , constantSpray, lone, Spray )
-import           Numeric.SpecFunctions      ( factorial )
-
--- | Symbolic Jack polynomial
-jackPol :: forall a. (Fractional a, Ord a, AR.C a) 
-  => Int -- ^ number of variables
-  -> Partition -- ^ partition of integers
-  -> a -- ^ alpha parameter
-  -> Spray a
-jackPol n lambda alpha =
-  case _isPartition lambda && alpha > 0 of
-    False -> if _isPartition lambda
-      then error "alpha must be strictly positive"
-      else error "lambda is not a valid integer partition"
-    True -> jac (length x) 0 lambda lambda arr0 1
-      where
-      nll = _N lambda lambda
-      x = map lone [1 .. n] :: [Spray a]
-      arr0 = listArray ((1, 1), (nll, n)) (replicate (nll * n) Nothing)
-      theproduct :: Int -> a
-      theproduct nu0 = if nu0 <= 1
-        then AR.one
-        else AR.product $ map (\i -> alpha * fromIntegral i + 1) [1 .. nu0-1]
-      jac :: Int -> Int -> Partition -> Partition -> Array (Int,Int) (Maybe (Spray a)) -> a -> Spray a
-      jac m k mu nu arr beta
-        | null nu || head nu == 0 || m == 0 = constantSpray 1
-        | length nu > m && nu!!m > 0 = constantSpray 0
-        | m == 1 = theproduct (head nu) *^ (head x ^**^ head nu) 
-        | k == 0 && isJust (arr ! (_N lambda nu, m)) =
-                      fromJust $ arr ! (_N lambda nu, m)
-        | otherwise = s
-          where
-            s = go (beta *^ (jac (m-1) 0 nu nu arr 1 ^*^ ((x!!(m-1)) ^**^ (sum mu - sum nu))))
-                (max 1 k)
-            go :: Spray a -> Int -> Spray a
-            go !ss ii
-              | length nu < ii || nu!!(ii-1) == 0 = ss
-              | otherwise =
-                let u = nu!!(ii-1) in
-                if length nu == ii && u > 0 || u > nu!!ii
-                  then
-                    let nu' = (element (ii-1) .~ u-1) nu in
-                    let gamma = beta * _betaratio' mu nu ii alpha in
-                    if u > 1
-                      then
-                        go (ss ^+^ jac m ii mu nu' arr gamma) (ii + 1)
-                      else
-                        if head nu' == 0
-                          then
-                            go (ss ^+^ (gamma *^ (x!!(m-1) ^**^ sum mu))) (ii + 1)
-                          else
-                            let arr' = arr // [((_N lambda nu, m), Just ss)] in
-                            let jck = jac (m-1) 0 nu' nu' arr' 1 in
-                            let jck' = gamma *^ (jck ^*^ 
-                                        (x!!(m-1) ^**^ (sum mu - sum nu'))) in
-                            go (ss ^+^ jck') (ii+1)
-                  else
-                    go ss (ii+1)
-
--- | Symbolic zonal polynomial
-zonalPol :: (Fractional a, Ord a, AR.C a) 
-  => Int -- ^ number of variables
-  -> Partition -- ^ partition of integers
-  -> Spray a
-zonalPol n lambda = c *^ jck
-  where
-    k = sum lambda
-    jlambda = product (hookLengths lambda 2)
-    c = 2^k * realToFrac (factorial k) / jlambda
-    jck = jackPol n lambda 2
-
--- | Symbolic Schur polynomial
-schurPol :: 
-  Int -- ^ number of variables
-  -> Partition -- ^ partition of integers
-  -> Spray Int
-schurPol n lambda =
-  case _isPartition lambda of
-    False -> error "lambda is not a valid integer partition"
-    True -> sch n 1 lambda arr0
-      where
-        x = map lone [1 .. n] :: [Spray Int]
-        nll = _N lambda lambda
-        arr0 = listArray ((1, 1), (nll, n)) (replicate (nll * n) Nothing)
-        sch :: Int -> Int -> [Int] -> Array (Int,Int) (Maybe (Spray Int)) -> Spray Int
-        sch m k nu arr
-          | null nu || head nu == 0 || m == 0 = constantSpray 1
-          | length nu > m && nu!!m > 0 = constantSpray 0
-          | m == 1 = head x ^**^ head nu
-          | isJust (arr ! (_N lambda nu, m)) = fromJust $ arr ! (_N lambda nu, m)
-          | otherwise = s
-            where
-              s = go (sch (m-1) 1 nu arr) k
-              go :: Spray Int -> Int -> Spray Int
-              go !ss ii
-                | length nu < ii || nu!!(ii-1) == 0 = ss
-                | otherwise =
-                  let u = nu!!(ii-1) in
-                  if length nu == ii && u > 0 || u > nu !! ii
-                    then
-                      let nu' = (element (ii-1) .~ u-1) nu in
-                      if u > 1
-                        then
-                          go (ss ^+^ ((x!!(m-1)) ^*^ sch m ii nu' arr)) (ii + 1)
-                        else
-                          if head nu' == 0
-                            then
-                              go (ss ^+^ (x!!(m-1))) (ii + 1)
-                            else
-                              let arr' = arr // [((_N lambda nu, m), Just ss)] in
-                              go (ss ^+^ ((x!!(m-1)) ^*^ sch (m-1) 1 nu' arr')) (ii + 1)
-                    else
-                      go ss (ii+1)
+{-|
+Module      : Math.Algebra.JackPol
+Description : Symbolic Jack polynomials.
+Copyright   : (c) Stéphane Laurent, 2024
+License     : GPL-3
+Maintainer  : laurent_step@outlook.fr
+
+Computation of symbolic Jack polynomials, zonal polynomials, and Schur polynomials. 
+See README for examples and references.
+-}
+
+{-# LANGUAGE BangPatterns        #-}
+{-# LANGUAGE ScopedTypeVariables #-}
+module Math.Algebra.JackPol
+  (jackPol, zonalPol, schurPol)
+  where
+import qualified Algebra.Ring               as AR
+import           Control.Lens               ( (.~), element )
+import           Data.Array                 ( Array, (!), (//), listArray )
+import           Data.Maybe                 ( fromJust, isJust )
+import           Math.Algebra.Jack.Internal ( _betaratio, hookLengths, _N
+                                            , _isPartition, Partition )
+import           Math.Algebra.Hspray        ( (*^), (^**^), (^*^), (^+^)
+                                            , lone, Spray
+                                            , zeroSpray, unitSpray )
+import           Numeric.SpecFunctions      ( factorial )
+
+-- | Symbolic Jack polynomial
+jackPol :: forall a. (Fractional a, Ord a, AR.C a) 
+  => Int       -- ^ number of variables
+  -> Partition -- ^ partition of integers
+  -> a         -- ^ alpha parameter
+  -> Spray a
+jackPol n lambda alpha =
+  case _isPartition lambda && alpha > 0 of
+    False -> if _isPartition lambda
+      then error "jackPol: alpha must be strictly positive"
+      else error "jackPol: invalid integer partition"
+    True -> jac (length x) 0 lambda lambda arr0 1
+      where
+      nll = _N lambda lambda
+      x = map lone [1 .. n] :: [Spray a]
+      arr0 = listArray ((1, 1), (nll, n)) (replicate (nll * n) Nothing)
+      theproduct :: Int -> a
+      theproduct nu0 = if nu0 <= 1
+        then 1
+        else product $ map (\i -> alpha * fromIntegral i + 1) [1 .. nu0-1]
+      jac :: Int -> Int -> Partition -> Partition -> Array (Int,Int) (Maybe (Spray a)) -> a -> Spray a
+      jac m k mu nu arr beta
+        | null nu || nu!!0 == 0 || m == 0 = unitSpray
+        | length nu > m && nu!!m > 0 = zeroSpray
+        | m == 1 = theproduct (nu!!0) *^ (x!!0 ^**^ nu!!0) 
+        | k == 0 && isJust (arr ! (_N lambda nu, m)) =
+                      fromJust $ arr ! (_N lambda nu, m)
+        | otherwise = s
+          where
+            s = go (beta *^ (jac (m-1) 0 nu nu arr 1 ^*^ ((x!!(m-1)) ^**^ (sum mu - sum nu))))
+                (max 1 k)
+            go :: Spray a -> Int -> Spray a
+            go !ss ii
+              | length nu < ii || nu!!(ii-1) == 0 = ss
+              | otherwise =
+                let u = nu!!(ii-1) in
+                if length nu == ii && u > 0 || u > nu!!ii
+                  then
+                    let nu' = (element (ii-1) .~ u-1) nu in
+                    let gamma = beta * _betaratio mu nu ii alpha in
+                    if u > 1
+                      then
+                        go (ss ^+^ jac m ii mu nu' arr gamma) (ii + 1)
+                      else
+                        if nu'!!0 == 0
+                          then
+                            go (ss ^+^ (gamma *^ (x!!(m-1) ^**^ sum mu))) (ii + 1)
+                          else
+                            let arr' = arr // [((_N lambda nu, m), Just ss)] in
+                            let jck = jac (m-1) 0 nu' nu' arr' 1 in
+                            let jck' = gamma *^ (jck ^*^ 
+                                        (x!!(m-1) ^**^ (sum mu - sum nu'))) in
+                            go (ss ^+^ jck') (ii+1)
+                  else
+                    go ss (ii+1)
+
+-- | Symbolic zonal polynomial
+zonalPol :: (Fractional a, Ord a, AR.C a) 
+  => Int       -- ^ number of variables
+  -> Partition -- ^ partition of integers
+  -> Spray a
+zonalPol n lambda = c *^ jck
+  where
+    k = sum lambda
+    jlambda = product (hookLengths lambda 2)
+    c = 2^k * realToFrac (factorial k) / jlambda
+    jck = jackPol n lambda 2
+
+-- | Symbolic Schur polynomial
+schurPol :: forall a. (Ord a, AR.C a)
+  => Int       -- ^ number of variables
+  -> Partition -- ^ partition of integers
+  -> Spray a
+schurPol n lambda =
+  case _isPartition lambda of
+    False -> error "schurPol: invalid integer partition"
+    True -> sch n 1 lambda arr0
+      where
+        x = map lone [1 .. n] :: [Spray a]
+        nll = _N lambda lambda
+        arr0 = listArray ((1, 1), (nll, n)) (replicate (nll * n) Nothing)
+        sch :: Int -> Int -> [Int] -> Array (Int,Int) (Maybe (Spray a)) -> Spray a
+        sch m k nu arr
+          | null nu || nu!!0 == 0 || m == 0 = unitSpray
+          | length nu > m && nu!!m > 0 = zeroSpray
+          | m == 1 = x!!0 ^**^ nu!!0
+          | isJust (arr ! (_N lambda nu, m)) = fromJust $ arr ! (_N lambda nu, m)
+          | otherwise = s
+            where
+              s = go (sch (m-1) 1 nu arr) k
+              go :: Spray a -> Int -> Spray a
+              go !ss ii
+                | length nu < ii || nu!!(ii-1) == 0 = ss
+                | otherwise =
+                  let u = nu!!(ii-1) in
+                  if length nu == ii && u > 0 || u > nu !! ii
+                    then
+                      let nu' = (element (ii-1) .~ u-1) nu in
+                      if u > 1
+                        then
+                          go (ss ^+^ ((x!!(m-1)) ^*^ sch m ii nu' arr)) (ii + 1)
+                        else
+                          if nu'!!0 == 0
+                            then
+                              go (ss ^+^ (x!!(m-1))) (ii + 1)
+                            else
+                              let arr' = arr // [((_N lambda nu, m), Just ss)] in
+                              go (ss ^+^ ((x!!(m-1)) ^*^ sch (m-1) 1 nu' arr')) (ii + 1)
+                    else
+                      go ss (ii+1)
diff --git a/tests/Main.hs b/tests/Main.hs
--- a/tests/Main.hs
+++ b/tests/Main.hs
@@ -1,65 +1,75 @@
-module Main where
-import           Data.Ratio
-import           Math.Algebra.Hspray
-import           Math.Algebra.Jack
-import           Math.Algebra.Jack.HypergeoPQ
-import           Math.Algebra.JackPol
-import           Math.HypergeoMatrix
-import           Test.Tasty                     ( defaultMain
-                                                , testGroup
-                                                )
-import           Test.Tasty.HUnit               ( assertEqual
-                                                , testCase
-                                                )
-
-main :: IO ()
-main = defaultMain $ testGroup
-
-  "Tests"
-
-  [ testCase "jackPol" $ do
-    let jp = jackPol 2 [3, 1] (2 % 1)
-        v  = evalSpray jp [1, 1]
-    assertEqual "" v (48 % 1)
-
-  , testCase "jack" $ do
-    assertEqual "" (jack [1, 1] [3, 1] (2 % 1)) (48 % 1)
-
-  , testCase "schurPol" $ do
-    let sp1 = schurPol 4 [4]
-        sp2 = schurPol 4 [3, 1]
-        sp3 = schurPol 4 [2, 2]
-        sp4 = schurPol 4 [2, 1, 1]
-        sp5 = schurPol 4 [1, 1, 1, 1]
-        v = evalSpray (sp1 ^+^ 3 *^ sp2 ^+^ 2 *^ sp3 ^+^ 3 *^ sp4 ^+^ sp5) [2, 2, 2, 2]
-    assertEqual "" v 4096
-
-  , testCase "schur" $ do
-    let sp1 = schur [1, 1, 1, 1] [4]
-        sp2 = schur [1, 1, 1, 1] [3, 1]
-        sp3 = schur [1, 1, 1, 1] [2, 2]
-        sp4 = schur [1, 1, 1, 1] [2, 1, 1]
-        sp5 = schur [1, 1, 1, 1] [1, 1, 1, 1]
-    assertEqual "" (sp1 + 3 * sp2 + 2 * sp3 + 3 * sp4 + sp5) 256
-
-  , testCase "zonalPol" $ do
-    let zp1 = zonalPol 4 [3]       :: Spray Rational
-        zp2 = zonalPol 4 [2, 1]    :: Spray Rational
-        zp3 = zonalPol 4 [1, 1, 1] :: Spray Rational
-        v   = evalSpray (zp1 ^+^ zp2 ^+^ zp3) [2, 2, 2, 2]
-    assertEqual "" v 512
-
-  , testCase "zonal" $ do
-    let zp1 = zonal [2 % 1, 2 % 1, 2 % 1, 2 % 1] [3]
-        zp2 = zonal [2 % 1, 2 % 1, 2 % 1, 2 % 1] [2, 1]
-        zp3 = zonal [2 % 1, 2 % 1, 2 % 1, 2 % 1] [1, 1, 1]
-    assertEqual "" (zp1 + zp2 + zp3) 512
-
-  , testCase "hypergeometric function" $ do
-    let a  = [1 % 1, 2 % 1]
-        b  = [3 % 1]
-        x  = [1 % 5, 1 % 2]
-        h1 = hypergeoPQ 10 a b x
-    h2 <- hypergeomat 10 2 a b x
-    assertEqual "" h1 h2
-  ]
+module Main where
+import Data.Ratio                               ( (%) )
+import Math.Algebra.Hspray                      ( (^+^), (*^), Spray
+                                                , evalSpray, isSymmetricSpray )
+import Math.Algebra.Jack                        ( jack, zonal, schur )
+import Math.Algebra.Jack.HypergeoPQ             ( hypergeoPQ )
+import Math.Algebra.JackPol                     ( zonalPol, jackPol, schurPol )
+import Math.HypergeoMatrix                      ( hypergeomat )
+import Test.Tasty                               ( defaultMain
+                                                , testGroup
+                                                )
+import Test.Tasty.HUnit                         ( assertEqual
+                                                , assertBool
+                                                , testCase
+                                                )
+
+main :: IO ()
+main = defaultMain $ testGroup
+
+  "Tests"
+
+  [ testCase "jackPol" $ do
+    let jp = jackPol 2 [3, 1] (2 % 1) :: Spray Rational
+        v  = evalSpray jp [1, 1]
+    assertEqual "" v (48 % 1)
+
+  , testCase "jackPol is symmetric" $ do
+    let jp = jackPol 3 [3, 2, 1] (2 % 1) :: Spray Rational
+    assertBool "" (isSymmetricSpray jp)
+
+  , testCase "jack" $ do
+    assertEqual "" (jack [1, 1] [3, 1] (2 % 1)) (48 % 1 :: Rational)
+
+  , testCase "schurPol" $ do
+    let sp1 = schurPol 4 [4]
+        sp2 = schurPol 4 [3, 1]
+        sp3 = schurPol 4 [2, 2]
+        sp4 = schurPol 4 [2, 1, 1]
+        sp5 = schurPol 4 [1, 1, 1, 1] :: Spray Int
+        v = evalSpray (sp1 ^+^ 3 *^ sp2 ^+^ 2 *^ sp3 ^+^ 3 *^ sp4 ^+^ sp5) [2, 2, 2, 2]
+    assertEqual "" v 4096
+
+  , testCase "schurPol is symmetric" $ do
+    let sp = schurPol 3 [3, 2, 1] :: Spray Rational
+    assertBool "" (isSymmetricSpray sp)
+
+  , testCase "schur" $ do
+    let sp1 = schur [1, 1, 1, 1] [4]
+        sp2 = schur [1, 1, 1, 1] [3, 1]
+        sp3 = schur [1, 1, 1, 1] [2, 2]
+        sp4 = schur [1, 1, 1, 1] [2, 1, 1]
+        sp5 = schur [1, 1, 1, 1] [1, 1, 1, 1] :: Int
+    assertEqual "" (sp1 + 3 * sp2 + 2 * sp3 + 3 * sp4 + sp5) 256
+
+  , testCase "zonalPol" $ do
+    let zp1 = zonalPol 4 [3]       :: Spray Rational
+        zp2 = zonalPol 4 [2, 1]    :: Spray Rational
+        zp3 = zonalPol 4 [1, 1, 1] :: Spray Rational
+        v   = evalSpray (zp1 ^+^ zp2 ^+^ zp3) [2, 2, 2, 2]
+    assertEqual "" v 512
+
+  , testCase "zonal" $ do
+    let zp1 = zonal [2 % 1, 2 % 1, 2 % 1, 2 % 1] [3]
+        zp2 = zonal [2 % 1, 2 % 1, 2 % 1, 2 % 1] [2, 1]
+        zp3 = zonal [2 % 1, 2 % 1, 2 % 1, 2 % 1] [1, 1, 1] :: Rational
+    assertEqual "" (zp1 + zp2 + zp3) 512
+
+  , testCase "hypergeometric function" $ do
+    let a  = [1 % 1, 2 % 1]
+        b  = [3 % 1]
+        x  = [1 % 5, 1 % 2]
+        h1 = hypergeoPQ 10 a b x :: Rational
+    h2 <- hypergeomat 10 2 a b x
+    assertEqual "" h1 h2
+  ]
