File ghc-runmemo.spec of Package ghc-runmemo

# spec file for package ghc-runmemo
# Copyright (c) 2016 SUSE LINUX GmbH, Nuernberg, Germany.
# All modifications and additions to the file contributed by third parties
# remain the property of their copyright owners, unless otherwise agreed
# upon. The license for this file, and modifications and additions to the
# file, is the same license as for the pristine package itself (unless the
# license for the pristine package is not an Open Source License, in which
# case the license is the MIT License). An "Open Source License" is a
# license that conforms to the Open Source Definition (Version 1.9)
# published by the Open Source Initiative.

# Please submit bugfixes or comments via

%global pkg_name runmemo
%bcond_with tests
Name:           ghc-%{pkg_name}
Release:        0
Summary:        A simple memoization helper library
License:        BSD-3-Clause
Group:          System/Libraries
Url:  {pkg_name}
BuildRequires:  ghc-Cabal-devel
BuildRequires:  ghc-rpm-macros
BuildRoot:      %{_tmppath}/%{name}-%{version}-build
# Begin cabal-rpm deps:
%if %{with tests}
BuildRequires:  ghc-data-memocombinators-devel
BuildRequires:  ghc-time-devel
# End cabal-rpm deps

This library encourages you to do memoization in three separate steps:

(1) Create a memoizable function

(2) Create or select an appropriate memoizer

(3) Run the memoizer on the memoizable function

Let's start with the first. When you create a memoizable function, you should
use the 'self' convention, which is that the first input to the function is
'self', and all recursive calls are replaced with 'self'. One common convention
that goes well with the 'self' convention is using a helper function 'go', like

' fib :: Memoizable (Integer -> Integer) fib self = go where go 0 = 1 go 1 = 1
go n = self (n-1) + self (n-2) '

Now for the second. For this example, we need a Memoizer that can handle an
'Integer' input, and an 'Integer' output. 'Data.MemoCombinators' provides
'integral', which handles any 'Integral' input, and any output.
'Data.MemoUgly' provides 'memo', which can memoize any function 'a -> b', given
an 'Ord' instance for 'a'.

Third, let's run our memoizers! Since we have decoupled the definition of the
memoized function from its actual memoization, we can create multiple memoized
versions of the same function if we so desire.

' import qualified Data.MemoUgly as Ugly import qualified Data.MemoCombinators
as MC

fibUgly :: Integer -> Integer fibUgly = runMemo Ugly.memo fib

fibMC :: Integer -> Integer fibMC = runMemo MC.integral fib '

You could easily do the same with 'Data.MemoTrie.memo',
'Data.Function.Memoize.memoize', etc.

Using this technique, you can create local memoized functions whose memo tables
are garbage collected as soon as they are no longer needed.

%package devel
Summary:        Haskell %{pkg_name} library development files
Group:          Development/Libraries/Other
Requires:       %{name} = %{version}-%{release}
Requires:       ghc-compiler = %{ghc_version}
Requires(post): ghc-compiler = %{ghc_version}
Requires(postun): ghc-compiler = %{ghc_version}

%description devel
This package provides the Haskell %{pkg_name} library development files.

%setup -q -n %{pkg_name}-%{version}



%if %{with tests}
%{cabal} test

%post devel

%postun devel

%files -f %{name}.files

%files devel -f %{name}-devel.files