The Autofac programming language is a new .NET based language (really an interpreter) that uses only Autofac constructor injection. Every command, literal, expression, etc is a type defined by constructor parameters. Program execution is defined by the order that the constructor values are resolved in. Inversion of control has never been so accessible!

Values are the core data types in AFPL. A value is always retrieved from an IValueProvider. To create a new value (including a new literal), simply create a new class that implements IValueProvider and implement string Provide(). This is modular and good separation of concerns - hardcoded literals inhibit testing, and now you can inject anything you want where previously you'd have to say Console.WriteLine("Hello World!").

Built-in values:

• NewLineValueProvider: provides a newline (specifically Environment.NewLine)
• ConcatValueProvider<TValueProvider1, TValueProvider2>: provides the concatenation of TValueProvider1 and TValueProvider2
• StackValueProvider: provides the top value from the program stack (without removing it)
• SecondStackValueProvider: provides the second-from-the-top value from the program stack (without removing it or the top value)
• RandomValueProvider: provides a random GUID

Commands tell the runtime what to do. You execute commands by placing them in order in the constructor of a type that is then resolved. If your program (the constructor signature) gets too long, you can easily break it apart by creating new types to inject.

Built-in commands:

• NoOp: does nothing
• PrintValue<TValueProvider>: prints the value returned from TValueProvider
• PrintValueNewLine<TValueProvider>: prints the value returned from TValueProvider followed by a newline
• PushValue<TValueProvider>: pushes the value returned from TValueProvider onto the program stack
• PopValue: pops the top value from the program stack
• PrintStackValue: prints the top value from the program stack without popping it
• ReadLine: reads a line from console input and places it onto the program stack
• If<TCondition, TSuccess, TElse>: if the conditional provided by TConditon evaluates to true, then it resolves (executes) TSuccess - otherwise it resolves (executes) TElse
• While<TCondition, TBody>: resolves (executes) TBody as long as TCondition evaluates to true

Conditionals implement ICondition. They have one must-implement method: bool Evaluate(). A conditional is true if Evaluate() returns true.

AFPL has the following built-in conditionals:

• Equals<TLeftValueProvider, TRightValueProvider>: true if the value provided by TLeftValueProvider equals the value provided by TRightValueProvider
• Equals<TLeftValueProvider>: true if the value provided by TLeftValueProvider is equal to the top value of the program stack
• StackEquals: true if the top value of the program stack is equal to the second-to-top value of the program stack
• NotEquals<TLeftValueProvider, TRightValueProvider>: true if the value provided by TLeftValueProvider does not equal the value provided by TRightValueProvider
• NotEquals<TLeftValueProvider>: true if the value provided by TLeftValueProvider is not equal to the top value of the program stack
• StackNotEquals: true if the top value of the program stack is not equal to the second-to-top value of the program stack
• GreaterThan<TLeftValueProvider, TRightValueProvider>: true if the value provided by TLeftValueProvider is greater than the value provided by TRightValueProvider
• GreaterThan<TLeftValueProvider>: true if the value provided by TLeftValueProvider is greater than to the top value of the program stack
• StackGreaterThan: true if the top value of the program stack is greater than the second-to-top value of the program stack
• LessThan<TLeftValueProvider, TRightValueProvider>: true if the value provided by TLeftValueProvider is less than the value provided by TRightValueProvider
• LessThan<TLeftValueProvider>: true if the value provided by TLeftValueProvider is less than to the top value of the program stack
• StackLessThan: true if the top value of the program stack is less than the second-to-top value of the program stack

See IsAndrewProgram.cs for an example of a program, or OverUnderProgram for a full-fledged number guessing game.

Why not?