Function

This library provides functions and effects, from 0- to 32-parameters, which support

• composition:

  final F1<String, Integer> length = String::length;
  final F1<String, Boolean> nonEmpty = length.then(i -> i > 0);
  assertFalse(nonEmpty.f(""));
  assertTrue(nonEmpty.f("abc"));

• constant function:

  final F1<String, Integer> constant0a = F1.constant(0);
  final F1<String, Integer> constant0b = F1.c(0);
  assertEquals(0, constant0a.f("abc"));
  assertEquals(0, constant0b.f("abc"));    

• identity function:

  final F1<Integer, Integer> id1 = F1.identity();
  final F1<Integer, Integer> id2 = F1.c();
  assertEquals(1, id1.f(1));
  assertEquals(1, id2.f(1));

• no-op effect:

  final E1<Integer> e1 = E1.nop();

• partial application:

  final F2<String, Character, Integer> indexOf = (string, character) -> string.indexOf(String.valueOf(character));
  final F1<Character, Integer> alphabetIndexOf = indexOf.a("abcdefghijklmnopqrstuvwxyz");
  assertEquals(0, alphabetIndexOf.f('a'));
  assertEquals(1, alphabetIndexOf.f('b'));

• reverse parameters:

  final F2<String, Character, Boolean> contains1 = (s, c) -> s.contains(String.valueOf(c));
  final F2<Character, String, Boolean> contains2 = contains1.reverse();
  assertTrue(contains1.f("abc", 'a'));
  assertTrue(contains2.f('a', "abc"));

• currying:

  final F2<String, Character, Boolean> contains1 = (s, c) -> s.contains(String.valueOf(c));
  final F1<String, F1<Character, Boolean>> contains2 = contains1.curry();
  assertTrue(contains1.f("abc", 'a'));
  assertTrue(contains2.f("abc").f('a'));

• uncurrying:

  final F1<String, F1<Character, Boolean>> contains1 = s -> c -> s.contains(String.valueOf(c));
  final F2<String, Character, Boolean> contains2 = F2.uncurry(contains1);
  assertTrue(contains1.f("abc").f('a'));
  assertTrue(contains2.f("abc", 'a'));

To Use

1. Update ~/.m2/settings.xml to include a github username or github email address and a github personal access token.

   For example:

   <settings>
       <servers>
           <server>
               <id>function</id>
               <username>github-username-or-email-address</username>
               <password>github-personal-access-token</password>
           </server>
       </servers>
   </settings>

2. Update pom.xml to include a reference to the repository.

   For example:

   <repositories>
       <repository>
           <id>function</id>
           <name>GitHub Packages</name>
           <url>https://maven.pkg.github.com/drewctaylor/function</url>
       </repository>
   </repositories>

3. Update pom.xml to include the dependency.

   For example:

   <dependencies>
       <dependency>
           <groupId>io.github.drewctaylor</groupId>
           <artifactId>function</artifactId>
           <version>1.0.0-SNAPSHOT</version>
       </dependency>
   </dependencies>