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# API Design Guidelines


# Introduction

The PayPal platform is a collection of reusable services that encapsulate well-defined business capabilities. Developers are encouraged to access these capabilities through Application Programming Interfaces (APIs) that enable consistent design patterns and principles. This facilitates a great developer experience and the ability to quickly compose complex business processes by combining multiple, complementary capabilities as building blocks.

PayPal APIs follow the [RESTful][0] architectural style as much as possible. To support our objectives, we have developed a set of rules, standards, and conventions that apply to the design of RESTful APIs. These have been used to help design and maintain hundreds of APIs and have evolved over several years to meet the needs of a wide variety of use cases.

We are sharing these guidelines to help propagate good API design practices in general. We have pulled extensively from the broader community and believe that it is importan

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JSONAPIObject:
  description: Includes the current JSON:API version for this specification as well as optional meta information
  type: object
  required:
    - version
  properties:
    version:
      type: string
      default: '1.0'
      example: '1.0'

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Applied Functional Programming with Scala - Notes

Copyright © 2016-2018 Fantasyland Institute of Learning. All rights reserved.

1. Mastering Functions

A function is a mapping from one set, called a domain, to another set, called the codomain. A function associates every element in the domain with exactly one element in the codomain. In Scala, both domain and codomain are types.

val square : Int => Int = x => x * x

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Code is clean if it can be understood easily – by everyone on the team. Clean code can be read and enhanced by a developer other than its original author. With understandability comes readability, changeability, extensibility and maintainability.

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General rules

1. Follow standard conventions.
2. Keep it simple stupid. Simpler is always better. Reduce complexity as much as possible.
3. Boy scout rule. Leave the campground cleaner than you found it.
4. Always find root cause. Always look for the root cause of a problem.

Design rules

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// === Basics
a must beMatching(bar)
a must be matching(bar)

a must not be matching(bar) // negation


// === Any object
a must_== b
a must_!= b