F# is an open-source functional programming language that can be used to write robust and performant code. This document introduces F# basics like syntax, data types, functions and modules. It also discusses the SAFE stack, which is a functional-first stack for building cloud-ready web applications using F# and other functional languages and frameworks. The document demonstrates building a TODO application using the SAFE stack to showcase its usage. It encourages readers to try F# and the SAFE stack for building applications in a functional paradigm.

1. 探索 .NET 新世界

2. F# & SAFE Stack
函數式開發典範
Kevin Yang

3. F# 基本介紹

4. 什麼是 F#
• An open-source language that makes it easy to write succinct,
robust, and performant code.
• Many features
• Lightweight syntax
• Immutable by default
• Type inference and automatic generalization
• First-class functions
• Powerful data types
• Pattern matching
• Async programming

5. 執行環境
• 安裝 .NET SDK 6 （支援 F# 6，有很多新功能)
• 編輯器選擇
• Visual Studio
• Visual Studio Code with【 Ionide-fsharp 】extension

6. Something about Function
• Simple Rule
• One input and return one output
• Pure function
• Given the same input, it will always return the same output.
Produces no side effects.
• Benefits
• easy to test
• cacheable
• parallelizable.

7. F# 語法介紹

8. Functions and modules
• Functions 是 F# 最基本元素
• 可用 Modules 來做分類管理
• 使用 open 來打開 module
• 使用 let 宣告 function
• 使用 let 綁定值到變數上 (Immutable)
• 使用 mutable 設定變數為 mutable
• 使用 <- 來改變值

9. Pipelines
• he pipe operator |> is used extensively when processing
data in F#.

10. Curried Functions
• Currying is a process that transforms a function that has
more than one parameter into a series of embedded
functions, each of which has a single parameter.

11. 型別
• 基礎型別
• string
• double quote
• string literal with @ or triple quote
• concatenation with +
• %s print a string value (type-safe)
• substrings use the indexer notation
• integer
• %d print an integer value (type-safe)
• float
• %f print a float value (type-safe)
• Boolean
• %b print a Boolean value (type-safe)

12. Tuples
• grouping of unnamed but ordered values
let tuple1 = (1, 2, 3)
let swapElems (a, b) = (b, a)

13. Lists, Arrays, Sequences
• Lists: ordered, immutable collections of elements of the same
type
• [ ] // empty list
• [1; 2; 3]
• [ 1 .. 10 ]
• Array: fixed-size, mutable collections of elements of the same
type
• [| |] // empty array
• 其餘的寫法跟 List 一樣
• Sequences: a logical series of elements, all of the same type
• Seq.empty // empty sequence
• seq { 1.. 10 }

14. Record
• an aggregate of named values, with optional members (such
as methods)
type ContactCard = { Name : string Phone : string Verified :
bool }
let contact1 = { Name = "Alf" Phone = "(206) 555-0157"
Verified = false }
let contact2 = { contact1 with Phone = "(206) 555-0112"
Verified = true }

15. Discriminated Unions
• values that could be a number of named forms or cases.
type Suit = | Hearts | Clubs | Diamonds | Spades
type Rank =
/// Represents the rank of cards 2 .. 10
| Value of int
| Ace
| King
| Queen
| Jack

16. Pattern Matching
• the F# feature that enables correctness for operating on F#
types.

17. Demo
Functional BDD

18. SAFE Stack

19. 什麼是 SAFE
• An end-to-end, functional-first stack for cloud-ready web
development that emphasizes type-safe programming
• .NET Core ready

20. 什麼是 SAFE
• Saturn + Giraffe for back-end services in F#
• Azure (Host) <= 為了拼出 SAFE 硬加上去的
• Fable for running F# in the web browser
• Elmish for client-side user interfaces

21. 使用 SAFE
• 安裝 SAFE project template (One time effort)
•
• 使用 safe project template
dotnet new –I SAFE.Template
dotnet new SAFE

22. Demo
TODO App with SAFE Stack

23. Take away
• F# is fun, you should try it sometime.
• FP 不難，只是他用另外一個角度思考問題罷了

24. References
• SAFE Documentation
• https://safe-stack.github.io/docs/template-overview/
• SAFE Demo Code
• https://github.com/chgc/FSharp-and-safe-demoCode-
dotnetConf2021
• F#
• https://fsharp.org/
• Functional BDD Demo Code
• https://github.com/chgc/example-functional-bdd-dotnetConf2021

25. Kevin Yang
• Blog
https://blog.kevinyang.net/
• FB Page
https://www.facebook.com/CKNotepad

26. Thanks for joining!

27. Azure Taiwan
User Group