# Bus 581

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Paradigm(s) | Functional |
---|---|

Designed by | User:Hakerh400 |

Appeared in | 2023 |

Computational class | Turing complete |

Major implementations | Uniplemented |

File extension(s) | `.txt` |

**Bus 581** is an esolang invented by User:Hakerh400 in 2023.

## Overview

This programming language is a derivative of the SKI combinator calculus. There are three combinators **K**, **S**, **T**, and the following rewriting rules:

K a b ---> a S a b c ---> a c (b c) T a ---> b

In the last reduction, for any combinator `a`

, if there exists some combinator `b`

such that `a b`

reduces to `K`

, then `T a`

reduces to one such `b`

(implementation-dependent which one, but it must be done consistently). If there is no such `b`

, then `T a`

reduces to any combinator `b`

(this also must be done consistently).

"Must be done consistently" means that for any fixed `a`

, the expression `T a`

always gives the same result.