# throne
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[crates_img]: https://img.shields.io/crates/v/throne.svg
[crates_link]: https://crates.io/crates/throne
A game scripting language for rapid prototyping and story logic:
```
// declare initial state as 'phrases', one phrase per line
happy
money 70
// define rules of the format: INPUT = OUTPUT
happy . money X . > X 50 . - X 50 Y = sad . money Y
// final state will be:
// sad
// money 20
```
Rules are of the format `INPUT = OUTPUT`, where `INPUT` and `OUTPUT` are lists that use period (`.`) as a separator between items:
- `INPUT` is a list of one or more conditions that must pass for the rule to be executed. The conditions can either be state phrases that must exist or predicates (such as `>`) that must evaluate to true. Any matching state phrases are consumed by the rule on execution.
- `OUTPUT` is a list of state phrases that will be generated by the rule if it is executed.
- Identifiers that use capital letters (`X` and `Y` in the snippet above) are variables that will be assigned when the rule is executed.
Evaluating a throne script involves executing any rule that matches the current state until the set of matching rules is exhausted. Rules are executed in a random order and may be executed more than once.
### Examples
- [blocks](examples/blocks.throne): a simple tile matching game
- Used in [Urban Gift](https://twitter.com/UrbanGiftGame/)
### Design
Strongly influenced by https://www.cs.cmu.edu/~cmartens/ceptre.pdf.