Functional Programming in Java with Lambda

Functional programming is a programming style that treats computation as the evaluation of mathematical functions and avoids changing-state and mutable data. It is a declarative programming paradigm in that programming is done with expressions or declarations instead of statements. For years, the conventional wisdom around attempting pure functional programming in Java has been “don’t”. There were plenty of good reasons: lambdas weren’t supported until the eighth major release of the language specification, creating value types is a verbose, ceremony-riddled exercise devoid of any first-class syntax, and neither are the majority of the data structures shipped in the JDK immutable, nor are interfaces a proper substitute in general for type classes.

Still, it’s a shame for developers to have to seemingly choose between the myriad benefits of functional programming and the maturity of the java compiler, the investments made into the ecosystem by major organizations, and the ease of hirability especially when some of these short-comings can be addressed externally. This talk presents Lambda, a Java library that offers:
* A first-class model for functors, applicative functors, monads, coproducts, and more algebraic and category theoretic structures
* Lazy evaluation
* Profunctor optics
* Semigroups and Monoids
* Type-safe heterogeneous structures like HLists and HMaps
* and more…

The goal of this talk is to present this library as a viable option for experienced Java development teams that wish they could use some functional programming capabilities available in languages like Haskell?, and to show how the trading infrastructure teams of an algorithmic-trading firm in Chicago use Lambda to write correct-by-construction software and accelerate their development process.

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