Scriptful

Scriptful is a minimalistic no_std stack machine for executing domain specific interpreted languages.

This library is heavily inspired by [FORTH] and Script, the scripting language in Bitcoin.

General design

The whole library is built around four main concepts:

• [Stack]: an ordered sequence of values that can be operated in a [LIFO]-alike way.
• [Item]: either a Value (a piece of data to be pushed into the stack) or an Operator (the descriptor for an action that operates on the topmost items in the stack).
• [Operator system]: a function that decides how each operator will mutate a given stack.
• [Script]: an ordered sequence of items (values and operators) that can be passed to an operator system for operating on a given stack.
• [Machine]: a convenient wrapper around a stack that enables multiple modes of operation.

Using this library is as easy as:

1. Defining your own set of operators, or using any of the ones that come bundled in the op_systems module.
2. Defining your own operator system function, or using any of the ones that come bundled in the op_systems module.
3. Instantiating a machine with a reference to your operator system.
4. Composing a script and running it in the machine.

Quick example

```rust use scriptful::prelude::; use scriptful::prelude::Value::;

[derive(Debug, PartialEq, Eq)]

/// You can define your own operators. enum MyOperator { Add, Equal, Sub, }

/// An operator system decides what to do with the stack when each operator is /// applied on it. fn myoperatorsystem(stack: &mut Stack, operator: &MyOperator) { match operator { MyOperator::Add => { let a = stack.pop(); let b = stack.pop(); stack.push(a + b); } MyOperator::Equal => { let a = stack.pop(); let b = stack.pop(); stack.push(Value::Boolean(a == b)); } MyOperator::Sub => { let a = stack.pop(); let b = stack.pop(); stack.push(a - b); } } }

// Instantiate the machine with a reference to your operator system. let mut machine = Machine::new(&myoperatorsystem);

// Run a script that simply adds 1 and 2 let result = machine.run_script(&[ Item::Value(Integer(1)), Item::Value(Integer(2)), Item::Operator(MyOperator::Add), ]);

// The result should unsurprisingly be 3 assert_eq!(*result, Integer(3)); ```

License

Scriptful is distributed under the terms of both the MIT license and the Apache License (Version 2.0).

See [LICENSE-APACHE] and [LICENSE-MIT], and [COPYRIGHT] for details.