Why functional programming matters
&gt; Imperative programming is like building assembly lines, which take some initial global state as raw material, apply various specific transformations, mutations to it as this material is pushed through the line, and at the end comes off the end product, the final global state, that represents the result of the computation.<p>This isn&#x27;t the best analogy as functional and imperative languages are both often used in a procedural fashion. If I simply replaced &quot;global state&quot; with &quot;immutable arguments&quot;, this analogy fits functional programming as well. The fact that the arguments would be copied, however, would be implied.<p>&gt; Each step needs to change, rotate, massage the workpiece precisely one specific way, so that it is prepared for subsequent steps downstream. Every step downstream depend on every previous step, and their order is therefore fixed and rigid.<p>This is more about tight coupling than imperative vs. functional paradigms. In general, imperative methods can be just as loosely coupled as functional methods. It basically comes down to what sort of data you&#x27;re handling.<p>&gt;  Because of these dependencies, an individual computational step has not much use and meaning in itself, but only in the context of all the others, and to understand it, one must understand how the whole line works.<p>This, again, can be true of functional languages as well. You cannot always guarantee that a method is individually useful given the data at hand.