Functional programming is the perfect Solution?

FUNCTIONAL PROGRAMMING

Functional programming is a style of programming that emphasizes writing applications using only pure functions and immutable values.

PURE FUNCTIONS

How we know that our code is pure functional or Impure , I’m putting some points on consideration

·         The function’s output depends only on its input variables

·         It doesn’t mutate any hidden state

·         It doesn’t have any “back doors”: It doesn’t read data from the outside world (including the console, web services, databases, files, etc.), or write data to the outside world

·         Example of pure function: scala.math._ package (abs,Ceil,max,min),Scala String Method(isEmpty,length,substring),Scala Collection(map,filter,drop)

Key Consideration:

A pure function is a function that depends only on its declared inputs and its internal algorithm to produce its output. It does not read any other values from “the outside world” — the world outside of the function’s scope — and it does not modify any values in the outside world.

impure functions:

the following functions are impure because they violate the definition.

The foreach method on collections classes is impure because it’s only used for its side effects, such as printing to STDOUT.

A great hint that foreach is impure is that it’s method signature declares that it returns the type Unit. Because it returns nothing, logically the only reason you ever call it is to achieve some side effect. Similarly, any method that returns Unit is going to be an impure function.

getDayOfWeek, getHour, and getMinute are all impure because their output depends on something other than their input parameters.

In general, impure functions do one or more of these things:

·         Read hidden inputs, i.e., they access variables and data not explicitly passed into the function as input parameters

·         Write hidden outputs

·         Mutate the parameters they are given

·         Perform some sort of I/O with the outside world

impure functions are needed …

Of course an application isn’t very useful if it can’t read or write to the outside world,

Write the core of your application using pure functions, and then write an impure “wrapper” around that core to interact with the outside world. If you like food analogies, this is like putting a layer of impure icing on top of a pure cake.

Key Consideration for Functional programming:

• Functional programmers don’t use null values
• A main replacement for null values is to use the Option/Some/None classes
• Common ways to work with Option values are match and for expressions
• Options can be thought of as containers of one item (Some) and no items (None)
• You can also use Options when defining constructor parameters