Haskell examples ⬆
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Directory examples\ contains Haskell code examples coming from various websites - mostly from the Haskell project.
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In the following we present the two examples Factorial and QuickSort.
We can build/run code examples in directory examples in several ways :
| Build tool | Build file | Parent file | Environment(s) |
|---|---|---|---|
cabal.exe |
Factorial.cabal |
n.a. | Any |
cmd.exe |
build.bat 1 |
n.a. | Windows only |
make.exe |
Makefile |
Makefile.inc |
Any |
mvn.cmd |
pom.xml |
pom.xml |
Any |
sh.exe |
build.sh |
Cygwin/MSYS2/Unix only | |
stack.exe |
stack.yaml |
n.a. | Any |
Factorial Example ▴
The directory structure of project Factorial looks as follows:
> cd H:\examples\Factorial > tree /a /f . | findstr /v "^[A-Z]" | .gitignore | .hlint.yaml | build.bat | build.sh | Factorial.cabal | Makefile | stack.yaml | Setup.hs | \---app Main.hs
Command cabal run all builds and executes the Haskell application (build file Factorial.cabal):
> where cabal C:\opt\ghc-8.10.7\bin\cabal.exe > cabal run all Resolving dependencies... Build profile: -w ghc-8.10.7 -O1 In order, the following will be built (use -v for more details): - Factorial-0.1.0.0 (exe:Factorial) (first run) Configuring executable 'Factorial' for Factorial-0.1.0.0.. Preprocessing executable 'Factorial' for Factorial-0.1.0.0.. Building executable 'Factorial' for Factorial-0.1.0.0.. [1 of 1] Compiling Main ( app\Main.hs, H:\examples\Factorial\dist-newstyle\build\x86_64-windows\ghc-8.10.7\Factorial-0.1.0.0\x\Factorial\build\Factorial\Factorial-tmp\Main.o ) Linking H:\examples\Factorial\dist-newstyle\build\x86_64-windows\ghc-8.10.7\Factorial-0.1.0.0\x\Factorial\build\Factorial\Factorial.exe ... factorialRec(5) =120 factorialRec2(5)=120 factorialFold(5)=120 factorialProd(5)=120
Command stack run builds and executes the Haskell application (build file stack.yaml):
> where stack C:\opt\stack-2.13.1\stack.exe > stack --silent run factorialRec(5) =120 factorialRec2(5)=120 factorialFold(5)=120 factorialProd(5)=120
🔎 We can build a profile-version of the project and execute the profile-instrumented Haskell application as follows:
> stack build --profile > stack exec target\dist\29cc6475\build\Factorial\Factorial.exe -- +RTS -p factorialRec(5) =120 factorialRec2(5)=120 factorialFold(5)=120 factorialProd(5)=120Profiling results are stored in file
Factorial.prof:> more Factorial.prof Tue Mar 03 22:21 2020 Time and Allocation Profiling Report (Final) Factorial.exe +RTS -p -RTS total time = 0.00 secs (0 ticks @ 1000 us, 1 processor) total alloc = 56,488 bytes (excludes profiling overheads) COST CENTRE MODULE SRC %time %alloc main Main app\Main.hs:(33,1)-(39,13) 0.0 36.0 CAF GHC.IO.Handle.FD <entire-module> 0.0 61.5 individual inherited COST CENTRE MODULE SRC no. entries %time %alloc %time %alloc MAIN MAIN <built-in> 125 0 0.0 0.9 0.0 100.0 CAF GHC.IO.Handle.Text <entire-module> 176 0 0.0 0.1 0.0 0.1 [..]
Command make -s run builds and executes the Haskell application (build file Makefile)
> where make C:\opt\make-3.81\bin\make.exe > make -s run factorialRec(5) =120 factorialRec2(5)=120 factorialFold(5)=120 factorialProd(5)=120
Command mvn -q compile exec:exec builds and executes the Haskell application (build file pom.xml)
> where mvn.cmd C:\opt\apache-maven\bin\mvn.cmd > mvn -q clean compile exec:exec [1 of 1] Compiling Main ( app\Main.hs, target\gen\Main.o ) Linking target/Main.exe ... factorialRec(5) =120 factorialRec2(5)=120 factorialFold(5)=120 factorialProd(5)=120
Command build clean run builds and executes the Haskell application (option -verbose prints progress messages) :
> where build H:\examples\Factorial\build.bat > build clean run factorialRec(5) =120 factorialRec2(5)=120 factorialFold(5)=120 factorialProd(5)=120
🔎 Commands
buildandmvnaccept one or more subcommands whilecabalandstackaccept only one. For instance the following command lines produce the same result:> build clean run > mvn clean compile exec:exec > cabal clean && cabal run all > stack clean && stack run
With option -debug command build also displays several useful informations, e.g.
- Execution environment : display actual value of properties, options, variables.
- Conditional processing : compile only if target is older than sources.
- Execution transparency : the executed console command with options and arguments can be copied/run separately.
> build -debug run [build] Properties : _PACKAGE_NAME=Factorial [build] Options : _TIMER=0 _VERBOSE=0 [build] Subcommands: _CLEAN=1 _COMPILE=1 _DOC=0 _LINT=0 _RUN=1 _TEST=0 [build] Variables : "CABAL_DIR=%APPDATA%\cabal" [build] Variables : "GHC_HOME=C:\opt\ghc-8.10.7" [build] 00000000000000 Target : "H:\examples\Factorial\target\Factorial.exe" [build] 20210208190257 Sources: "H:\examples\Factorial\app\*.hs" [build] _ACTION_REQUIRED=1 [build] ghc.exe -Wall -Werror -o "H:\examples\Factorial\target\Main.exe" -hidir "H:\examples\Factorial\target\gen" -odir "H:\examples\Factorial\target\gen" "H:\examples\Factorial\app\Main.hs" [1 of 1] Compiling Main ( H:\examples\Factorial\app\Main.hs, H:\examples\Factorial\target\gen\Main.o ) Linking H:\examples\Factorial\target\Main.exe ... [build] H:\examples\Factorial\target\Main.exe factorialRec(5) =120 factorialRec2(5)=120 factorialFold(5)=120 factorialProd(5)=120 [build] _EXITCODE=0
QuickSort Example ▲
The directory structure of project QuickSort looks as follows:
> cd H:\examples\QuickSort > tree /a /f . | findstr /v "^[A-Z]" | .gitignore | build.bat | build.sh | QuickSort.cabal | Setup.hs | stack.yaml | \---app Main.hs
Command cabal run all builds and executes the Haskell application (build file QuickSort.cabal):
> where cabal C:\opt\ghc-8.10.7\bin\cabal.exe > cabal clean && cabal run all Resolving dependencies... Build profile: -w ghc-8.10.7 -O1 In order, the following will be built (use -v for more details): - QuickSort-0.1.0.0 (exe:QuickSort) (first run) Configuring executable 'QuickSort' for QuickSort-0.1.0.0.. Preprocessing executable 'QuickSort' for QuickSort-0.1.0.0.. Building executable 'QuickSort' for QuickSort-0.1.0.0.. [1 of 1] Compiling Main ( app\Main.hs, H:\examples\QuickSort\dist-newstyle\build\x86_64-windows\ghc-8.10.7\QuickSort-0.1.0.0\x\QuickSort\build\QuickSort\QuickSort-tmp\Main.o ) Linking H:\examples\QuickSort\dist-newstyle\build\x86_64-windows\ghc-8.10.7\QuickSort-0.1.0.0\x\QuickSort\build\QuickSort\QuickSort.exe ... input list : [8,4,0,3,1,23,11,18] sorted(filter) : [0,1,3,4,8,11,18,23] sorted(list comp): [0,1,3,4,8,11,18,23]
Command stack run builds and executes the Haskell application (build file stack.yaml):
> where stack C:\opt\stack-2.13.1\stack.exe > stack clean && stack --silent run input list : [8,4,0,3,1,23,11,18] sorted(filter) : [0,1,3,4,8,11,18,23] sorted(list comp): [0,1,3,4,8,11,18,23]
Command make -s run builds and executes the Haskell application (build file Makefile)
> make -s run input list : [8,4,0,3,1,23,11,18] sorted(filter) : [0,1,3,4,8,11,18,23] sorted(list comp): [0,1,3,4,8,11,18,23] sorted(ST) : [0,1,3,4,8,11,18,23]
Command mvn -q compile exec:exec builds and executes the Haskell application (build file pom.xml)
> mvn -q clean compile exec:exec [1 of 1] Compiling Main ( app\Main.hs, target\gen\Main.o ) Linking target/Main.exe ... input list : [8,4,0,3,1,23,11,18] sorted(filter) : [0,1,3,4,8,11,18,23] sorted(list comp): [0,1,3,4,8,11,18,23]
Command build clean run builds and executes the Haskell application:
> where build H:\examples\QuickSort\build.bat > build clean run input list : [8,4,0,3,1,23,11,18] sorted(filter) : [0,1,3,4,8,11,18,23] sorted(list comp): [0,1,3,4,8,11,18,23]
With option -debug command build also displays several useful informations, e.g.
- Execution environment : display actual value of properties, options, variables.
- Conditional processing : compile only if target is older than sources.
- Execution transparency : the executed console command with options and arguments can be copied/run separately.
> build -debug run [build] Properties : _PACKAGE_NAME=Factorial [build] Options : _TIMER=0 _VERBOSE=0 [build] Subcommands: _CLEAN=0 _COMPILE=1 _DOC=0 _LINT=0 _RUN=1 _TEST=0 [build] Variables : "CABAL_DIR=%APPDATA%\cabal" [build] Variables : "GHC_HOME=C:\opt\ghc-8.10.7" [build] 00000000000000 Target : "H:\examples\Factorial\target\Factorial.exe" [build] 20210208190257 Sources: "H:\examples\Factorial\app\*.hs" [build] _ACTION_REQUIRED=1 [build] "C:\opt\ghc-8.10.7\bin\ghc.exe" -Wall -Wmissing-import-lists -Wincomplete-uni-patterns -Werror -hidir "H:\examples\Factorial\target\gen" -odir "H:\examples\Factorial\target\gen" -o "H:\examples\Factorial\target\Factorial.exe" "H:\examples\Factorial\app\Main.hs" Loaded package environment from %APPDATA%\ghc\x86_64-mingw32-8.10.7\environments\default [1 of 1] Compiling Main ( H:\examples\Factorial\app\Main.hs, H:\examples\Factorial\target\gen\Main.o ) Linking H:\examples\Factorial\target\Factorial.exe ... [build] "H:\examples\Factorial\target\Factorial.exe" factorialRec(5) =120 factorialRec2(5)=120 factorialFold(5)=120 factorialProd(5)=120 [build] _EXITCODE=0
Footnotes ▴
[1] build.bat ↩
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In project
Factorialthe batch filebuild.batreads several properties directly fromFactorial.cabalif the Cabal project file is present; for instance:name,synopsis,versionandghc_options.