F# is a functional-first programming language developed by Microsoft and used extensively in financial analysis and financial applications. F# expert developer Kit Eason steps you through the process of developing a simple F# financial application: a Twitter bot that charts stock price changes and respond to tweets with some simple descriptors of the stock performance, including gain/loss and highs/lows. Along the way, you'll learn the basics of F# syntax, including values, arrays, functions, and expressions, and how to test your code, analyze and chart third-party data. The lessons also provide a primer to concepts like test-driven development and railway-oriented programming—best practices for any F# development workflow.