This is a partial port of the Ramda.js functional programming library to work with vavr types.

v0.0.11 (experimental, incomplete)

Adding it to your project

Maven

It's not on Maven Central yet, but you can find it in JCenter. First, add JCenter to the repositories in your pom:

    <repositories>
        <repository>
            <id>jcenter</id>
            <url>http://jcenter.bintray.com </url>
        </repository>
    </repositories>

Then you can import it as usual:

    <dependencies>
        <dependency>
            <groupId>de.michaelzinn.ravr</groupId>
            <artifactId>ravr</artifactId>
            <version>0.0.11</version>
        </dependency>
    </dependencies>

Gradle

compile 'de.michaelzinn.ravr:ravr:0.0.11'

Curried functions & partial function application

Ravr provides two ways to do partial application: Either leave out parameters at the end or use a parameter placeholder:

// All the same
List.of(1, 2, 3).map(x -> add(2, x));
List.of(1, 2, 3).map(add(2, __)); // works but isn't idiomatic
List.of(1, 2, 3).map(add(2)); // use this one instead
// => [3, 4, 5]

// The placeholder should only be used when necessary.
List.of(7, 8, 9).map(subtract(__, 2));
// => [5, 6, 7]

Function composition

You can compose functions in two ways.

Compose

Similar to mathematical composition. This is a vararg function.

// classic Java
map(add(1).compose(multiply(2)).compose(subtract(__, 1)), List(2, 3, 4));
// => [3, 5, 7]

// Ravr style
map(compose(add(1), multiply(2), subtract(__, 1)), List(1, 2, 3));
// => [3, 5, 7]

Pipe

Same as compose, but with the order inverted. This can be more readable when putting functions on separate lines.

List<String> words = List.of("xSIHTx", "xSIx", "xGNITSERETNIx");

assertThat(
	join("... ", words.map(pipe(
		Ravr::reverse,
		Ravr::toLower,
		Ravr::init,
		Ravr::tail
	))),
	is("this... is... interesting")
);

Functor, Applicative, Monad

Ravr provides map, ap, and flatMap.

Pattern	Standard name	Ramda name	Ravr name	Type signature
Functor	map	map	map	Functor m => (a -> b) -> m a -> m b
Applicative	apply	ap	ap	Applicative m => m (a -> b) -> m a -> m b
Monad	bind	chain	flatMap	Monad m => (a -> m b) -> m a -> m b

Due to limits in Java's type system these currently only work on Lists, Options, Traversables and Futures.

Lenses (experimental)

Lenses only work on types that implement the included Copyable interface, which is a simplified version of the Cloneable interface. The simplest way to implement it is wrapping the clone function:

@Getters // lombok
@Setters // lombok
@AllArgsConstructor // lombok
class Thing implements Copyable<Thing> {
	String name;
	int quality;

	@Override
        public Thing copy() {
            return safeClone(() -> clone());
        }
}

Note: Your IDE might tell you to replace the lambda with a method reference. This might not work because of reasons.

You can create a lens using a pair of getters and setters. You can use the lens in combination with get, set and over:

Lens<Thing, String> name = lens(Thing::getName, Thing::setName);
Lens<Thing, Integer> quality = lens(Thing::getQuality, Thing::setQuality);

Thing lookingGlass = new Thing("looking glass", 5);

get(name, lookingGlass); // "looking glass"

Function1<Thing, Thing>
improve = pipe(
	set(name, "ten times better"),
	over(quality, multiply(10))
);

Thing betterThing = improve.apply(lookingGlass);

get(quality, betterThing); // 50
get(quality, lookingGlass); // 5 (not changed)

Other functions

You can concatenate the content of a List<Option<X>> to List<X> with the concatOptions function.

List<String> strings = List(">>>>", "", "====");

pipe(
	head(),	// List.of(Option.some(">"), Option.none(), Option.some("="))
	concatOptions(),	// List.of(">", "=")
	join(">")	// ">>="
).apply(strings);

What's included

Icon	Meaning
✅	Works
😐	Works with issues
	Not implemented
✖️	Not planned
💠	Bonus function not originally included in Ramda.js

This list is generated automatically and slightly inaccurate right now.

Status	Function	Note
✅	add
	addIndex
✅	adjust
✅	all
	allPass
✅	always
	and
✅	any
	anyPass
✅	ap
	aperture
✅	append
✅	apply
	applySpec
✅	ap_List
✅	ap_Option
✅	apᐸListᐳ
✅	apᐸOptionᐳ
	ascend
	assoc
✖️	assocPath
	binary
	bind
	both
	call
	chain
	clamp
✖️	clone
	comparator
✅	complement
	compose
	composeK
	composeP
✅	concat
💠	concatOptions
	cond
	construct
	constructN
✅	contains
	converge
💠	count
	countBy
	curry
	curryN
✅	dec
✅	defaultTo
	descend
	difference
	differenceWith
	dissoc
	dissocPath
	divide
	drop
	dropLast
	dropLastWhile
	dropRepeats
	dropRepeatsWith
	dropWhile
	either
	empty
	endsWith
✅	eq
	eqBy
	eqProps
	equals
	evolve
	F
✅	filter
	find
✅	findIndex
	findLast
	findLastIndex
✅	flatMap
✅	flatMap_List
✅	flatMap_Option
✅	flatMapᐸListᐳ
✅	flatMapᐸOptionᐳ
	flatten
	flip
✅	forEach
	forEachObjIndexed
	fromPairs
✅	get
✅	groupBy
	groupWith
	gt
	gte
	has
	hasIn
✅	head
✅	head_String
✅	headᐸStringᐳ
	identical
✅	identity
✅	ifElse
✅	inc
	indexBy
	indexOf
	init
	innerJoin
	insert
	insertAll
	intersection
	intersectionWith
	intersperse
	into
	invert
	invertObj
	invoker
	is
	isEmpty
	isNil
✅	isNone	Replacement for isNil, returns true for Option.none().
✅	isSome	Replacement for complement(isNil), returns true for Option.some("whatever").
✅	join
💠	joinOption	Like join, except that it returns nothing when joining empty lists.
	juxt
	keys
	keysIn
	last
	lastIndexOf
	length
✅	lens
	lensIndex
	lensPath
	lensProp
	lift
	liftN
	lt
	lte
✅	map
	mapAccum
	mapAccumRight
💠	mapLeft	Maps the left side of an Either
💠	mapLeft_Either
💠	mapLeftᐸEitherᐳ
	mapObjIndexed
✅	map_Either
✅	map_List
✅	map_Option
✅	mapᐸEitherᐳ
✅	mapᐸListᐳ
✅	mapᐸOptionᐳ
	match
	mathMod
	max
	maxBy
	mean
	median
	memoize
	memoizeWith
	merge
	mergeAll
	mergeDeepLeft
	mergeDeepRight
	mergeDeepWith
	mergeDeepWithKey
	mergeWith
	mergeWithKey
	min
	minBy
	modulo
	multiply
	nAry
	negate
✅	none
✅	not
	nth
	nthArg
✅	nullTo
	o
	objOf
	of
	omit
	once
	or
✅	over
	pair
	partial
	partialRight
	partition
	path
	pathEq
	pathOr
	pathSatisfies
	pick
	pickAll
	pickBy
	pipe
	pipeK
	pipeP
	pluck
✅	prepend
	product
	project
	prop
	propEq
	propIs
	propOr
	props
	propSatisfies
✅	range
💠	rangeC	Closed range
	reduce
	reduceBy
	reduced
	reduceRight
	reduceWhile
	reject
	remove
😐	repeat	Can't be curried.
	replace
✅	reverse
	scan
	sequence
✅	set
	slice
	sort
✅	sortBy
	sortWith
	split
	splitAt
	splitEvery
	splitWhen
	startsWith
	subtract
	sum
	symmetricDifference
	symmetricDifferenceWith
	T
✅	tail
	take
	takeLast
	takeLastWhile
	takeWhile
	tap
	test
	times
✅	toLower
	toPairs
	toPairsIn
	toString
✅	toUpper
	transduce
	transpose
	traverse
	trim
	tryCatch
✖️	type
	unapply
	unary
	uncurryN
	unfold
	union
	unionWith
	uniq
	uniqBy
	uniqWith
	unless
	unnest
	until
	update
	useWith
	values
	valuesIn
	view
	when
	where
	whereEq
✅	without
	xprod
✅	zip
	zipObj
✅	zipWith
	_isArrayLike

Future plans

Other Ramda functions will be added as needed.

Contributing

The scope of this library is to port Ramda. Extra functions like concatOptions should be the exception. Contact me on Twitter.

Licensed under the LGPL v3, see the LICENSE file for details.