# blc
**blc** is an implementation of the
[binary lambda calculus](https://esolangs.org/wiki/Binary_lambda_calculus).
## Binary lambda calculus basics
Binary lambda calculus (BLC) is a minimal, purely functional programming language based on a binary
encoding of the untyped [lambda calculus](https://en.wikipedia.org/wiki/Lambda_calculus) with
[De Bruijn indices](https://en.wikipedia.org/wiki/De_Bruijn_index).
Lambda terms have the following representation in BLC:
| abstraction | λM | 00M |
| application | MN | 01MN |
| variable | i | 1<sup>i</sup>0 |
Since BLC programs are basically lambda calculus terms, they can be applied to other terms. In
order to be applicable to binary (but not BLC-encoded) input, it has to be lambda-encoded first.
Bytestrings are lambda-encoded as
[Church lists](https://en.wikipedia.org/wiki/Church_encoding#One_pair_as_a_list_node) of bytes
and bytes are lambda-encoded as Church lists of lambda-encoded bits.
Bits 0 and 1 are lambda-encoded as
[Church booleans](https://en.wikipedia.org/wiki/Church_encoding#Church_Booleans):
| 0 | λλ2 (true) | 0000110 |
| 1 | λλ1 (false) | 000010 |
Example: BLC-encoding steps for a byte representing the ASCII/UTF-8 encoded letter 'a':
| decimal | 96 |
| binary | 01100001 |
| lambda | λ1(<b>λλ2</b>)(λ1(<b>λλ1</b>)(λ1(<b>λλ1</b>)(λ1(<b>λλ2</b>)(λ1(<b>λλ2</b>)(λ1(<b>λλ2</b>)(λ1(<b>λλ2</b>)(λ1(<b>λλ1</b>)(λλ1)))))))) |
| BLC | 0001011000010110<b>0000110</b>00010110<b>000010</b>00010110<b>000010</b>00010110<b>0000110</b>00010110<b>0000110</b>00010110<b>0000110</b>00010110<b>0000110</b>00010110<b>000010</b>000010000010 |
## [Documentation](https://docs.rs/blc)
## Status
The library is already usable, but it is still a work in progress.
## TODO
- better documentation
- more blc examples