├── .circleci └── config.yml ├── .gitignore ├── LICENSE ├── README.md ├── build.gradle ├── gradle └── wrapper │ ├── gradle-wrapper.jar │ └── gradle-wrapper.properties ├── gradlew ├── gradlew.bat └── src ├── main └── kotlin │ └── either │ └── Either.kt └── test └── kotlin └── either └── EitherTest.kt /.circleci/config.yml: -------------------------------------------------------------------------------- 1 | version: 2 2 | 3 | jobs: 4 | build: 5 | working_directory: ~/work 6 | 7 | docker: 8 | - image: circleci/openjdk:11 9 | 10 | steps: 11 | - checkout 12 | 13 | - restore_cache: 14 | key: cache-{{ checksum "build.gradle" }}-{{ checksum "gradle/wrapper/gradle-wrapper.properties" }} 15 | 16 | - run: ./gradlew test 17 | 18 | - save_cache: 19 | paths: 20 | - ~/.gradle 21 | key: cache-{{ checksum "build.gradle" }}-{{ checksum "gradle/wrapper/gradle-wrapper.properties" }} 22 | 23 | - store_test_results: 24 | path: build/test-results 25 | -------------------------------------------------------------------------------- /.gitignore: -------------------------------------------------------------------------------- 1 | .gradle 2 | build/ 3 | out/ 4 | 5 | # Ignore Gradle GUI config 6 | gradle-app.setting 7 | 8 | # Avoid ignoring Gradle wrapper jar file (.jar files are usually ignored) 9 | !gradle-wrapper.jar 10 | 11 | # Cache of project 12 | .gradletasknamecache 13 | 14 | .idea/ 15 | *.iml 16 | -------------------------------------------------------------------------------- /LICENSE: -------------------------------------------------------------------------------- 1 | The MIT License (MIT) 2 | 3 | Copyright (c) 2016 Nizamutdinov Adel 4 | 5 | Permission is hereby granted, free of charge, to any person obtaining a copy 6 | of this software and associated documentation files (the "Software"), to deal 7 | in the Software without restriction, including without limitation the rights 8 | to use, copy, modify, merge, publish, distribute, sublicense, and/or sell 9 | copies of the Software, and to permit persons to whom the Software is 10 | furnished to do so, subject to the following conditions: 11 | 12 | The above copyright notice and this permission notice shall be included in all 13 | copies or substantial portions of the Software. 14 | 15 | THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR 16 | IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 17 | FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE 18 | AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER 19 | LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, 20 | OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE 21 | SOFTWARE. 22 | -------------------------------------------------------------------------------- /README.md: -------------------------------------------------------------------------------- 1 | # kotlin-either 2 | 3 | An Either type for you to fold all day, [inspired by scalaz](https://github.com/scalaz/scalaz/blob/master/core/src/main/scala/scalaz/Either.scala) 4 | 5 | 6 | ## Installation 7 | 8 | [![](https://jitpack.io/v/adelnizamutdinov/kotlin-either.svg)](https://jitpack.io/#adelnizamutdinov/kotlin-either) 9 | 10 | ```groovy 11 | repositories { 12 | maven { url "https://jitpack.io" } 13 | } 14 | dependencies { 15 | compile "com.github.adelnizamutdinov:kotlin-either:$version" 16 | } 17 | ``` 18 | 19 | 20 | ## Usage 21 | 22 | [See tests for usage examples](src/test/kotlin/either/EitherTest.kt) 23 | 24 | 25 | [![CircleCI](https://circleci.com/gh/adelnizamutdinov/kotlin-either.svg?style=svg)](https://circleci.com/gh/adelnizamutdinov/kotlin-either) 26 | -------------------------------------------------------------------------------- /build.gradle: -------------------------------------------------------------------------------- 1 | plugins { 2 | id 'org.jetbrains.kotlin.jvm' version "1.3.72" 3 | id "com.github.ben-manes.versions" version "0.28.0" 4 | } 5 | 6 | compileKotlin { 7 | kotlinOptions { 8 | jvmTarget = JavaVersion.VERSION_1_6 9 | allWarningsAsErrors = true 10 | } 11 | } 12 | compileTestKotlin { 13 | kotlinOptions { 14 | jvmTarget = JavaVersion.VERSION_11 15 | } 16 | } 17 | 18 | repositories { 19 | mavenCentral() 20 | } 21 | 22 | dependencies { 23 | compileOnly "org.jetbrains.kotlin:kotlin-stdlib" 24 | 25 | testImplementation( 26 | "org.jetbrains.kotlin:kotlin-test-junit5", 27 | "org.junit.jupiter:junit-jupiter-engine:5.7.0-M1", 28 | ) 29 | } 30 | 31 | java { 32 | withSourcesJar() 33 | } 34 | 35 | test { 36 | useJUnitPlatform() 37 | } 38 | -------------------------------------------------------------------------------- /gradle/wrapper/gradle-wrapper.jar: -------------------------------------------------------------------------------- https://raw.githubusercontent.com/meoyawn/kotlin-either/9389298b21adc93dd1279e21d0a3f63011c937f2/gradle/wrapper/gradle-wrapper.jar -------------------------------------------------------------------------------- /gradle/wrapper/gradle-wrapper.properties: -------------------------------------------------------------------------------- 1 | #Wed Mar 09 20:44:41 MSK 2016 2 | distributionBase=GRADLE_USER_HOME 3 | distributionPath=wrapper/dists 4 | zipStoreBase=GRADLE_USER_HOME 5 | zipStorePath=wrapper/dists 6 | distributionUrl=https\://services.gradle.org/distributions/gradle-6.5-all.zip 7 | -------------------------------------------------------------------------------- /gradlew: -------------------------------------------------------------------------------- 1 | #!/usr/bin/env bash 2 | 3 | ############################################################################## 4 | ## 5 | ## Gradle start up script for UN*X 6 | ## 7 | ############################################################################## 8 | 9 | # Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script. 10 | DEFAULT_JVM_OPTS="" 11 | 12 | APP_NAME="Gradle" 13 | APP_BASE_NAME=`basename "$0"` 14 | 15 | # Use the maximum available, or set MAX_FD != -1 to use that value. 16 | MAX_FD="maximum" 17 | 18 | warn ( ) { 19 | echo "$*" 20 | } 21 | 22 | die ( ) { 23 | echo 24 | echo "$*" 25 | echo 26 | exit 1 27 | } 28 | 29 | # OS specific support (must be 'true' or 'false'). 30 | cygwin=false 31 | msys=false 32 | darwin=false 33 | case "`uname`" in 34 | CYGWIN* ) 35 | cygwin=true 36 | ;; 37 | Darwin* ) 38 | darwin=true 39 | ;; 40 | MINGW* ) 41 | msys=true 42 | ;; 43 | esac 44 | 45 | # Attempt to set APP_HOME 46 | # Resolve links: $0 may be a link 47 | PRG="$0" 48 | # Need this for relative symlinks. 49 | while [ -h "$PRG" ] ; do 50 | ls=`ls -ld "$PRG"` 51 | link=`expr "$ls" : '.*-> \(.*\)$'` 52 | if expr "$link" : '/.*' > /dev/null; then 53 | PRG="$link" 54 | else 55 | PRG=`dirname "$PRG"`"/$link" 56 | fi 57 | done 58 | SAVED="`pwd`" 59 | cd "`dirname \"$PRG\"`/" >/dev/null 60 | APP_HOME="`pwd -P`" 61 | cd "$SAVED" >/dev/null 62 | 63 | CLASSPATH=$APP_HOME/gradle/wrapper/gradle-wrapper.jar 64 | 65 | # Determine the Java command to use to start the JVM. 66 | if [ -n "$JAVA_HOME" ] ; then 67 | if [ -x "$JAVA_HOME/jre/sh/java" ] ; then 68 | # IBM's JDK on AIX uses strange locations for the executables 69 | JAVACMD="$JAVA_HOME/jre/sh/java" 70 | else 71 | JAVACMD="$JAVA_HOME/bin/java" 72 | fi 73 | if [ ! -x "$JAVACMD" ] ; then 74 | die "ERROR: JAVA_HOME is set to an invalid directory: $JAVA_HOME 75 | 76 | Please set the JAVA_HOME variable in your environment to match the 77 | location of your Java installation." 78 | fi 79 | else 80 | JAVACMD="java" 81 | which java >/dev/null 2>&1 || die "ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH. 82 | 83 | Please set the JAVA_HOME variable in your environment to match the 84 | location of your Java installation." 85 | fi 86 | 87 | # Increase the maximum file descriptors if we can. 88 | if [ "$cygwin" = "false" -a "$darwin" = "false" ] ; then 89 | MAX_FD_LIMIT=`ulimit -H -n` 90 | if [ $? -eq 0 ] ; then 91 | if [ "$MAX_FD" = "maximum" -o "$MAX_FD" = "max" ] ; then 92 | MAX_FD="$MAX_FD_LIMIT" 93 | fi 94 | ulimit -n $MAX_FD 95 | if [ $? -ne 0 ] ; then 96 | warn "Could not set maximum file descriptor limit: $MAX_FD" 97 | fi 98 | else 99 | warn "Could not query maximum file descriptor limit: $MAX_FD_LIMIT" 100 | fi 101 | fi 102 | 103 | # For Darwin, add options to specify how the application appears in the dock 104 | if $darwin; then 105 | GRADLE_OPTS="$GRADLE_OPTS \"-Xdock:name=$APP_NAME\" \"-Xdock:icon=$APP_HOME/media/gradle.icns\"" 106 | fi 107 | 108 | # For Cygwin, switch paths to Windows format before running java 109 | if $cygwin ; then 110 | APP_HOME=`cygpath --path --mixed "$APP_HOME"` 111 | CLASSPATH=`cygpath --path --mixed "$CLASSPATH"` 112 | JAVACMD=`cygpath --unix "$JAVACMD"` 113 | 114 | # We build the pattern for arguments to be converted via cygpath 115 | ROOTDIRSRAW=`find -L / -maxdepth 1 -mindepth 1 -type d 2>/dev/null` 116 | SEP="" 117 | for dir in $ROOTDIRSRAW ; do 118 | ROOTDIRS="$ROOTDIRS$SEP$dir" 119 | SEP="|" 120 | done 121 | OURCYGPATTERN="(^($ROOTDIRS))" 122 | # Add a user-defined pattern to the cygpath arguments 123 | if [ "$GRADLE_CYGPATTERN" != "" ] ; then 124 | OURCYGPATTERN="$OURCYGPATTERN|($GRADLE_CYGPATTERN)" 125 | fi 126 | # Now convert the arguments - kludge to limit ourselves to /bin/sh 127 | i=0 128 | for arg in "$@" ; do 129 | CHECK=`echo "$arg"|egrep -c "$OURCYGPATTERN" -` 130 | CHECK2=`echo "$arg"|egrep -c "^-"` ### Determine if an option 131 | 132 | if [ $CHECK -ne 0 ] && [ $CHECK2 -eq 0 ] ; then ### Added a condition 133 | eval `echo args$i`=`cygpath --path --ignore --mixed "$arg"` 134 | else 135 | eval `echo args$i`="\"$arg\"" 136 | fi 137 | i=$((i+1)) 138 | done 139 | case $i in 140 | (0) set -- ;; 141 | (1) set -- "$args0" ;; 142 | (2) set -- "$args0" "$args1" ;; 143 | (3) set -- "$args0" "$args1" "$args2" ;; 144 | (4) set -- "$args0" "$args1" "$args2" "$args3" ;; 145 | (5) set -- "$args0" "$args1" "$args2" "$args3" "$args4" ;; 146 | (6) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" ;; 147 | (7) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" "$args6" ;; 148 | (8) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" "$args6" "$args7" ;; 149 | (9) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" "$args6" "$args7" "$args8" ;; 150 | esac 151 | fi 152 | 153 | # Split up the JVM_OPTS And GRADLE_OPTS values into an array, following the shell quoting and substitution rules 154 | function splitJvmOpts() { 155 | JVM_OPTS=("$@") 156 | } 157 | eval splitJvmOpts $DEFAULT_JVM_OPTS $JAVA_OPTS $GRADLE_OPTS 158 | JVM_OPTS[${#JVM_OPTS[*]}]="-Dorg.gradle.appname=$APP_BASE_NAME" 159 | 160 | exec "$JAVACMD" "${JVM_OPTS[@]}" -classpath "$CLASSPATH" org.gradle.wrapper.GradleWrapperMain "$@" 161 | -------------------------------------------------------------------------------- /gradlew.bat: -------------------------------------------------------------------------------- 1 | @if "%DEBUG%" == "" @echo off 2 | @rem ########################################################################## 3 | @rem 4 | @rem Gradle startup script for Windows 5 | @rem 6 | @rem ########################################################################## 7 | 8 | @rem Set local scope for the variables with windows NT shell 9 | if "%OS%"=="Windows_NT" setlocal 10 | 11 | @rem Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script. 12 | set DEFAULT_JVM_OPTS= 13 | 14 | set DIRNAME=%~dp0 15 | if "%DIRNAME%" == "" set DIRNAME=. 16 | set APP_BASE_NAME=%~n0 17 | set APP_HOME=%DIRNAME% 18 | 19 | @rem Find java.exe 20 | if defined JAVA_HOME goto findJavaFromJavaHome 21 | 22 | set JAVA_EXE=java.exe 23 | %JAVA_EXE% -version >NUL 2>&1 24 | if "%ERRORLEVEL%" == "0" goto init 25 | 26 | echo. 27 | echo ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH. 28 | echo. 29 | echo Please set the JAVA_HOME variable in your environment to match the 30 | echo location of your Java installation. 31 | 32 | goto fail 33 | 34 | :findJavaFromJavaHome 35 | set JAVA_HOME=%JAVA_HOME:"=% 36 | set JAVA_EXE=%JAVA_HOME%/bin/java.exe 37 | 38 | if exist "%JAVA_EXE%" goto init 39 | 40 | echo. 41 | echo ERROR: JAVA_HOME is set to an invalid directory: %JAVA_HOME% 42 | echo. 43 | echo Please set the JAVA_HOME variable in your environment to match the 44 | echo location of your Java installation. 45 | 46 | goto fail 47 | 48 | :init 49 | @rem Get command-line arguments, handling Windows variants 50 | 51 | if not "%OS%" == "Windows_NT" goto win9xME_args 52 | if "%@eval[2+2]" == "4" goto 4NT_args 53 | 54 | :win9xME_args 55 | @rem Slurp the command line arguments. 56 | set CMD_LINE_ARGS= 57 | set _SKIP=2 58 | 59 | :win9xME_args_slurp 60 | if "x%~1" == "x" goto execute 61 | 62 | set CMD_LINE_ARGS=%* 63 | goto execute 64 | 65 | :4NT_args 66 | @rem Get arguments from the 4NT Shell from JP Software 67 | set CMD_LINE_ARGS=%$ 68 | 69 | :execute 70 | @rem Setup the command line 71 | 72 | set CLASSPATH=%APP_HOME%\gradle\wrapper\gradle-wrapper.jar 73 | 74 | @rem Execute Gradle 75 | "%JAVA_EXE%" %DEFAULT_JVM_OPTS% %JAVA_OPTS% %GRADLE_OPTS% "-Dorg.gradle.appname=%APP_BASE_NAME%" -classpath "%CLASSPATH%" org.gradle.wrapper.GradleWrapperMain %CMD_LINE_ARGS% 76 | 77 | :end 78 | @rem End local scope for the variables with windows NT shell 79 | if "%ERRORLEVEL%"=="0" goto mainEnd 80 | 81 | :fail 82 | rem Set variable GRADLE_EXIT_CONSOLE if you need the _script_ return code instead of 83 | rem the _cmd.exe /c_ return code! 84 | if not "" == "%GRADLE_EXIT_CONSOLE%" exit 1 85 | exit /b 1 86 | 87 | :mainEnd 88 | if "%OS%"=="Windows_NT" endlocal 89 | 90 | :omega 91 | -------------------------------------------------------------------------------- /src/main/kotlin/either/Either.kt: -------------------------------------------------------------------------------- 1 | package either 2 | 3 | sealed class Either { 4 | data class Left(val value: T) : Either() 5 | data class Right(val value: T) : Either() 6 | } 7 | 8 | inline fun Either.fold(left: (L) -> T, right: (R) -> T): T = 9 | when (this) { 10 | is Either.Left -> left(value) 11 | is Either.Right -> right(value) 12 | } 13 | 14 | inline fun Either.flatMap(f: (R) -> Either): Either = 15 | fold(left = { this as Either.Left }, right = f) 16 | 17 | inline fun Either.map(f: (R) -> T): Either = 18 | flatMap { Either.Right(f(it)) } 19 | -------------------------------------------------------------------------------- /src/test/kotlin/either/EitherTest.kt: -------------------------------------------------------------------------------- 1 | package either 2 | 3 | import org.junit.jupiter.api.Test 4 | import kotlin.test.assertEquals 5 | 6 | class EitherTest { 7 | 8 | private companion object { 9 | 10 | fun left(value: T): Either = 11 | Either.Left(value) 12 | 13 | fun right(value: T): Either = 14 | Either.Right(value) 15 | } 16 | 17 | @Test 18 | fun map() { 19 | assertEquals( 20 | actual = left(5).map { it + "yes" }, 21 | expected = Either.Left(5) 22 | ) 23 | 24 | assertEquals( 25 | actual = right(5).map { it * 5 }, 26 | expected = Either.Right(25) 27 | ) 28 | } 29 | 30 | @Test 31 | fun flatMap() { 32 | assertEquals( 33 | actual = left(5).flatMap { left(it + "yes") }, 34 | expected = Either.Left(5) 35 | ) 36 | 37 | assertEquals( 38 | actual = right(5).flatMap { left(it * 5) }, 39 | expected = Either.Left(25) 40 | ) 41 | } 42 | 43 | @Test 44 | fun fold() { 45 | assertEquals( 46 | actual = left(5).fold({ "left" }, { "right" }), 47 | expected = "left" 48 | ) 49 | 50 | assertEquals( 51 | actual = right(5).fold({ "left" }, { "right" }), 52 | expected = "right" 53 | ) 54 | } 55 | } 56 | --------------------------------------------------------------------------------