Loda

Features

Functional programming in Dart and Flutter.

Getting started

The loda module is a combination of the two Lodash and Ramda modules. It promotes a more functional programming (FP) friendly style by exporting an instance of loda with its methods wrapped to produce immutable auto-curried iteratee-first data-last methods.

Installation

install

# pubspec.yaml
dependencies:
  loda: ^1.0.3

Placeholder

Placeholder is a helper class that allows defining mathematical comparisons as functions.

Operators

• >= (num b): Returns a function that checks if a number is greater than or equal to b.
• > (num b): Returns a function that checks if a number is greater than b.
• <= (num b): Returns a function that checks if a number is less than or equal to b.
• < (num b): Returns a function that checks if a number is less than b.

Pipeline

The Pipeline<T, R> class is used for function composition and chaining.

Methods

• then<S>(S Function(R) next): Chains another function to transform the output.
• thenEither<L, S>(Either<L, S> Function(R) next): Chains a function that returns an Either type.
• call(T input): Executes the pipeline on an input.

Extensions for Either

• mapEitherRight<S>(S Function(R) f): Transforms the Right value of Either.
• mapEitherLeft<L2>(L2 Function(L) f): Transforms the Left value of Either.
• mapEitherBoth<L2, S>(L2 Function(L) f1, S Function(R) f2): Transforms both Left and Right values.

Functional Programming Utilities (FP)

A collection of functional programming utilities under FP.

Functions

• pipe<T>(): Creates an identity pipeline.
• chainEither<L, T, R>(Either<L, T> either, Pipeline<T, R> pipeline): Applies a pipeline to an Either value.

Predicate Utilities

• and<T>(List<Predicate<T>> predicates): Combines multiple predicates using logical AND.
• or<T>(List<Predicate<T>> predicates): Combines multiple predicates using logical OR.

Filtering and Mapping

• filter<T>(bool Function(T) predicate): Filters a list based on a predicate.
• filterIndex<T>(bool Function(int, T) predicate): Filters a list based on the index and value.
• filterMap<K, V>(bool Function(K, V) predicate): Filters a map based on key-value pairs.
• map<T, R>(R Function(T) mapper): Maps over a list.
• mapIndex<T, R>(R Function(int, T) mapper): Maps over a list with index values.
• mapMap<K, V, K2, V2>(MapEntry<K2, V2> Function(K, V) mapper): Maps over a map.
• flatMap<T, R>(Iterable<R> Function(T) mapper): Maps and flattens a list.

Distinct Operations

• distinct<T>(): Removes duplicates from a list.
• distinctMap<K, V>(): Removes duplicate entries from a map.

Usage

final isPositive = (int x) => x > 0;
final isEven = (int x) => x % 2 == 0;

final check = FP.and([isPositive, isEven]);
print(check(4)); // true
print(check(-2)); // false

Additional information

My article introduces to Functional Programming LINK