introduction to functional programming in scala

Functional Programming with ScalaIntroduction by @JacekLaskowski

Jacek Laskowski@JacekLaskowskihttp://blog.japila.pl

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Functional programmingIn computer science, functional programming

is a programming paradigm that treats computation as the evaluation of

mathematical functions and avoids state and mutable data. It emphasizes the application of

functions, in contrast to the imperative programming style, which emphasizes changes in state.

HTTP://EN.WIKIPEDIA.ORG/WIKI/FUNCTIONAL_PROGRAMMING

Functional programming•Programming paradigm

•Computation = function evaluation

•Avoids state and mutable data

•Function composition

•Expressions everywhere

Scala is a modern multi-paradigm programming language designed to express common programming patterns in a concise, elegant, and type-safe way. It smoothly integrates features of object-oriented and functional languages.

HTTP://WWW.SCALA-LANG.ORG/NODE/104

Scala is also a functional language in the sense that every function is a value.

Keyword to define a Method

Method’s name

Method’s input parameters and

their typesMethod’s

return type (optional)

Method’s body

Expression vs statement

•A statement changes state•it’s called for side effects

•An expression produces result

FROM “ATOMIC SCALA” BY BRUCE ECKEL AND DIANNE MARSH

Everything in Scala is an expression

Is this an expression?

YES!Is this an expression?

YES!

Type => TypeFunction type

Function type examples

•Int => String•(Int, Int) => Int•Int => Int => Int•(Int => Int) => Int

Scala REPL

Collections in Scala

•Vector

•Set

•Map

•Range

Functional trio

•map

•filter

•reduce (foldLeft + foldRight)

Function literal

Function composition

Jacek Laskowski@JacekLaskowskihttp://blog.japila.pl

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