ThrowAway

ThrowAway is a pragmatic and efficient C# library that marries functional programming concepts with traditional procedural error handling. It is designed to elegantly manage the dichotomy between successful outcomes (Values) and error states (Failures) by leveraging the power of the Option type. This hybrid approach makes it easy to write expressive, functional code while still integrating seamlessly with conventional try-catch exception handling.

Overview

In many C# applications, error handling is either bogged down by traditional exception logic or forced into a rigid functional style. ThrowAway bridges these two worlds by offering:

• Explicit Functional Handling: Model success and failure as first-class citizens with Option types.
• Seamless Procedural Integration: Implicit conversions let you work with Options as if they were plain values - while automatically throwing a HasFailedException when an Option is in a failed state. This allows you to mix functional transformations with traditional try-catch error management.

Key Features

• Dual Outcomes: Every operation returns an Option that encapsulates either a valid result (Value) or an error (Failure).
• Implicit Conversions: Options automatically convert to their underlying type. When an Option represents a failure, an exception is thrown, enabling smooth integration with procedural exception handling.
• Rich Functional API: A suite of extension methods (like Map, FlatMap, Match, Filter, Transpose, and Use) enables chaining and composing operations in a functional style.
• No Nulls: Being struct-based, Options guarantee non-null instances, improving type safety.
• Hybrid Error Handling: Combines the explicitness of functional error handling with the convenience of procedural exception handling.
• Robust Exception Wrapping: Methods like CatchFailure and CatchAll convert exceptions into failed Options, maintaining consistency in error handling.
• Seamless Unwrapping: TryUnwrap lets you extract both the value and the failure message without additional boilerplate.

Two Flavors: Option (Maybe) vs. Option (Either)

ThrowAway provides two variants of the Option type:

1. Option (Maybe)
   This variant fixes the failure type to a string. It's ideal when a simple error message suffices.
   Usage Example:

   // Creating a successful Option (Maybe)
   Option<int> maybeSuccess = Option.Some(100);
   
   // Creating a failed Option (Maybe)
   Option<int> maybeFailure = Option.Fail("Invalid input");
   
   // Implicit conversion and exception handling:
   try {
       int value = maybeSuccess; // Works fine
   }
   catch (HasFailedException<string> ex) {
       Console.WriteLine($"Failure: {ex.Failure}");
   }

2. Option (Either)
   This variant is generic in its failure type, allowing you to provide richer or more structured error information.
   Usage Example:

   // Creating a successful Option (Either) with a custom failure type:
   Option<double, MyError> eitherSuccess = Option.Some<double, MyError>(3.14);
   
   // Creating a failed Option (Either) with a custom error:
   Option<double, MyError> eitherFailure = Option.Fail<double, MyError>(new MyError("Calculation error"));
   
   // Implicit conversion; note that an exception of type HasFailedException<MyError> is thrown on failure:
   try {
       double result = eitherSuccess;
   }
   catch (HasFailedException<MyError> ex) {
       Console.WriteLine($"Error: {ex.Failure}");
   }

In the above examples, MyError can be any type you define to represent error details, giving you the flexibility to carry structured error information.

Exception Handling with CatchFailure and CatchAll

ThrowAway offers two powerful methods to encapsulate exception handling within your functional flow:

• CatchFailure:
  Executes a function that returns an Option. If a HasFailedException occurs (i.e., a known failure within the Option chain), it converts the exception into a failed Option.

• CatchAll:
  This method is more comprehensive. It catches both HasFailedException instances and any unexpected exceptions, converting them into a failed Option complete with the exception message and stack trace. This helps maintain a consistent error handling model without the need for manual try-catch blocks around every operation.

Example:

// Using CatchFailure to wrap operations that may throw a HasFailedException
var result = Option.CatchFailure(() => ProcessData());

// Using CatchAll to capture any exception and convert it into a failure Option
var resultWithAll = Option.CatchAll(() => ProcessData(), errorMsg => $"Custom Error: {errorMsg}");

Using TryUnwrap for Seamless Extraction

The TryUnwrap extension method lets you extract both the success value and the failure message in one go - without needing extra temporary variables. This method returns a boolean indicating whether the Option holds a value and outputs the value and failure as separate out parameters.

if (areaResult.TryUnwrap(out double area, out string failure))
{
    // Use the value directly.
    Console.WriteLine($"Area is: {area}");
}
else
{
    // Handle the failure.
    Console.WriteLine($"Error calculating area: {failure}");
}

This feature is especially useful in procedural code, as it eliminates boilerplate and provides immediate access to both outcomes.

Installation

Install ThrowAway via NuGet:

dotnet add package ThrowAway

Usage Examples

Basic Option Usage

Handling operations that might succeed or fail is straightforward:

// Option (Maybe) usage:
var maybeOutcome = Option.Some(5);
var maybeError = Option.Fail("An error occurred");

// Option (Either) usage:
var eitherOutcome = Option.Some<int, string>(42);
var eitherError = Option.Fail<int, string>("Calculation failed");

Implicit Conversion and Exception Handling

Implicit conversion makes the integration with try-catch blocks seamless:

try
{
    int result = Option.Some(10); // Implicitly converts to int.
    Console.WriteLine($"Result: {result}");
}
catch (HasFailedException<string> ex)
{
    Console.WriteLine($"Error: {ex.Failure}");
}

Combining Functional and Procedural Styles

A typical example where functional chaining meets procedural checks:

public Option<double> CalculateArea(double length, double width)
{
    if (length <= 0 || width <= 0)
        return "Invalid dimensions provided";
    
    return length * width;
}

var areaResult = CalculateArea(10, 5);
if (areaResult.HasFailed)
{
    Console.WriteLine($"Error: {areaResult.Failure}");
}
else
{
    // Implicit conversion to double
    double area = areaResult;
    Console.WriteLine($"Area: {area}");
}

Advanced Functional Operations

Chain transformations and error handling with ThrowAway's rich API:

var finalResult = Option.Some(5)
    .Map(x => x * 2)
    .FlatMap(x => x > 10 
        ? Option.Some(x.ToString()) 
        : Option.Fail<string>("Result is too small"))
    .Match(
        some: val => $"Success: {val}",
        fail: err => $"Failure: {err}"
    );
Console.WriteLine(finalResult);

Why Choose ThrowAway?

• Pragmatic Integration:
  Benefit from explicit functional error handling while continuing to use familiar procedural constructs like try-catch.
• Clear Code Paths:
  Clearly distinguish between success and failure, making your code easier to understand and maintain.
• Eliminate Nulls:
  Struct-based Options guarantee non-null instances, reducing the risk of null-reference errors.
• Flexible API:
  Whether you need simple string errors (Option Maybe) or more detailed error types (Option Either), ThrowAway has you covered.
• Robust Exception Wrapping:
  CatchFailure and CatchAll methods convert exceptions into failed Options, keeping error handling consistent.
• Effortless Unwrapping:
  TryUnwrap simplifies the extraction of values and failures, bridging the gap between functional and procedural paradigms.

License

ThrowAway is licensed under the MIT License, making it an open and flexible solution for error handling in both open-source and commercial projects.