《Composing SoftWare》

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Composing Software author: Eric Elliott

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Composing Functions

Function composition is the process of applying the function to the output of another function.

Working Memory

Signal Noise To Ratio

Concise code can improve the signal-to-noise ratio of your code.

Surface Area For Bugs

less code = less the surface area for bugs = fewer bugs

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Composing Object

There are primitives:

const firstName = "gold"
const lastName = "eli"

This is a composite:

const obj = {
  firstName: "gold"
  lastName: "eli"
}

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The Dao of immutability

Dao: Data Acess Object

Immutability

erase history

Separation

Flow

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The Rise And Fall And Rise Of The Functional Programming

The rise of functional programming

lisp

The fall of functional programming

java c++ 1980~2010

inheritance hierarchies

The rise of functional programming

Javascript explosion

The array functions were like rocket fuel for function programming explosion in Javascript.

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App ate the world, The browser ate the app, JavaScript ate the browser.

By multiple measure, Javascript is one of the most popular languages in the world.

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At any given moment, there are close to a hundred thousand job openings in the united states and hundreds of thousands job in more world-wide.

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Function

Functions may serve the following purpose:

• mapping
• Procederg
• I/O

Pure Function

• process the input return the output. Given the same input, will always return the same output.
• Produce no side effect

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We can grasp the meaning of functional programming:

• Pure Functions
• Function Composition
• Avoid shared state
• Avoid mutating state
• Avoid side effects