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: a simple tile matching game
• Used in an upcoming game

Design

Strongly influenced by https://www.cs.cmu.edu/~cmartens/ceptre.pdf.