Simon Painter

Down the Oregon Trail with Functional C#

What if the Oregon Trail's messy GOTO logic could become a clean, monadic pipeline? See how functional C# transforms a classic game into modern, testable code.

Down the Oregon Trail with Functional C#
#1about 5 minutes

Core principles of the functional programming paradigm

Functional programming is a declarative style emphasizing immutability, pure functions, and expressions over statements to write more testable and robust code.

#2about 2 minutes

Applying the umbra and penumbra metaphor to C#

Achieve nearly pure functional code by isolating necessary compromises, like I/O, to the outer edges (penumbra) of the application.

#3about 3 minutes

The historical context behind the Oregon Trail game

The game is based on the 19th-century migration of settlers in covered wagons from the US East Coast to Oregon.

#4about 7 minutes

How BASIC and time-sharing enabled interactive games

The creation of the user-friendly BASIC language and time-sharing terminals at Dartmouth University led to a boom in early computer games.

#5about 4 minutes

Analyzing the original 1975 Oregon Trail BASIC code

The original game's logic is built on line numbers, GOTO statements, and reversed IF conditions, which requires careful translation.

#6about 11 minutes

Handling impure user input with discriminated unions

Manage the side effects of console input by wrapping results in a `Maybe` type, a discriminated union representing `Something`, `Nothing`, or `Error` states.

#7about 5 minutes

Replacing indefinite loops with a functional helper

Avoid imperative `while` loops for input validation by using a recursive `iterate until` helper function that encapsulates the looping logic.

#8about 2 minutes

Structuring the main game loop with a monadic flow

Chain game events together using a `continue game` extension method that checks the game state before executing the next function, simplifying the main loop.

#9about 1 minute

Recreating the time-based hunting mini-game functionally

Implement the time-sensitive "type BANG" mechanic by injecting a time service to enable pure, testable functions for calculating shot accuracy.

#10about 3 minutes

Refactoring complex conditional logic with switch expressions

Replace the original game's convoluted, nested IF statements for rider encounters with a clean and readable C# switch expression.

#11about 3 minutes

Exploring other classic text-based games to remake

Consider other classic text-based games like Star Trek, Doctor Who, and Zork as potential future projects for functional programming exercises.

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