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let rec fibonacci n =
if n = 0 then 0
elif n = 1 then 1
else fibonacci(n-1) + fibonacci(n-2)
[0..9] |> List.iter (fun n -> printfn "%d" (fibonacci n))Coding works best on desktop or with an external keyboard.
F# Fibonacci Sequence - Fsharp Typing CST Test
F# Fibonacci Sequence — Fsharp Code
Recursive Fibonacci sequence generator.
let rec fibonacci n =
if n = 0 then 0
elif n = 1 then 1
else fibonacci(n-1) + fibonacci(n-2)
[0..9] |> List.iter (fun n -> printfn "%d" (fibonacci n))Fsharp Language Guide
F# is a functional-first, strongly typed language on the .NET platform. It blends functional, object-oriented, and imperative styles, offering concise syntax, powerful type inference, and high reliability. Ideal for data science, finance, domain modeling, and backend services.
Primary Use Cases
- ▸Financial modeling and trading systems
- ▸Data science and ML workflows
- ▸Backend microservices on .NET
- ▸Domain-driven design (DDD)
- ▸Scientific computation
- ▸Scripting & automation
- ▸High-reliability enterprise applications
Notable Features
- ▸Functional-first design
- ▸Type inference
- ▸Pattern matching
- ▸Algebraic data types (DU’s)
- ▸Immutable defaults
- ▸Interop with .NET languages
Origin & Creator
Developed by Microsoft Research under Don Syme, released in 2005 as a functional-first language on .NET.
Industrial Note
F# excels in enterprise financial analytics, domain-driven modeling, algorithmic trading systems, scientific computation, ML/AI pipelines, data engineering, and strongly typed business rule engines where correctness and expressiveness are crucial.
Quick Explain
- ▸F# is functional-first but supports OOP and imperative features.
- ▸Runs on .NET, giving access to the entire .NET ecosystem.
- ▸Popular in finance, data engineering, scientific computing, and reliable backend services.
Core Features
- ▸Expressions over statements
- ▸Powerful type inference
- ▸Discriminated unions
- ▸Pattern matching everywhere
- ▸Pipelining with
- ▸Async workflows
Learning Path
- ▸Functional thinking basics
- ▸DU’s, records, modules
- ▸Pipelines & pattern matching
- ▸Async workflows
- ▸Domain modeling & DDD
Practical Examples
- ▸Domain modeling with DU’s
- ▸Financial risk calculator
- ▸Async HTTP service
- ▸Data pipeline workflow
- ▸ML.NET model integration
Comparisons
- ▸More concise than C#
- ▸More enterprise-ready than Python
- ▸More type-safe than JavaScript
- ▸Less concurrency-focused than Elixir
- ▸More accessible tooling than Haskell
Strengths
- ▸Concise & expressive code
- ▸Enterprise-grade reliability on .NET
- ▸Strong static typing with inference
- ▸Excellent for domain modeling
- ▸Great for data processing & analysis
Limitations
- ▸Smaller community than C#/Python
- ▸Not ideal for UI-heavy applications
- ▸Learning curve for functional thinking
- ▸Corporate teams often prefer C#
- ▸Tooling is improving but not perfect
When NOT to Use
- ▸Frontend UI-heavy apps
- ▸Games requiring Unity/C# workflow
- ▸Projects with large C#-only teams
- ▸Tiny scripts (Python is simpler)
- ▸GPU-heavy ML workloads
Cheat Sheet
- ▸Record: type Person = { Name: string; Age: int }
- ▸DU: type Shape = Circle of float
- ▸Match: match x with
- ▸Pipe: x
- ▸Async: async { let! r = fetch(); return r }
FAQ
- ▸Is F# used in industry?
- ▸Yes-especially in finance, modeling, and enterprise systems.
- ▸Is F# only functional?
- ▸No-functional-first but supports OOP & imperative code.
- ▸Is F# better than C# for some tasks?
- ▸Yes-functional modeling, data pipelines, and correctness-heavy logic.
- ▸Is F# good for beginners?
- ▸Yes-concise syntax and strong type inference help beginners a lot.
30-Day Skill Plan
- ▸Week 1: Syntax, lists, functions
- ▸Week 2: DU’s, records, modules
- ▸Week 3: Async workflows, data pipelines
- ▸Week 4: Real-world app + DDD
Final Summary
- ▸F# is a powerful functional-first language on .NET.
- ▸It is ideal for finance, data pipelines, scientific computation, and enterprise architecture.
- ▸Its expressive type system and concise syntax make modeling complex domains easy.
- ▸F# combines functional elegance with industrial-grade performance.
Project Structure
- ▸Program.fs (entry point)
- ▸Library modules in separate .fs files
- ▸.fsproj config
- ▸paket.dependencies / nuget
- ▸tests/ folder
Monetization
- ▸Financial engineering roles
- ▸Data science consulting
- ▸SaaS backend development
- ▸Algorithmic trading systems
Productivity Tips
- ▸Use pipelines aggressively
- ▸Model domains with DU’s
- ▸Use REPL for rapid exploration
- ▸Use records for clarity
Basic Concepts
- ▸Immutability
- ▸Discriminated unions
- ▸Record types
- ▸Sequences, lists, arrays
- ▸Pattern matching
- ▸Pipelines & higher-order functions
Official Docs
- ▸F# Official Documentation
- ▸.NET API Browser
- ▸F# Software Foundation