# BLoC

This project proposes a file format for programs encoded in binary
lambda calculus. Its main goal is minimal redundancy and therefore
allowing maximal optimization.

It’s kind of inspired by ELF.

## Format

It’s assumed that all bit-encoded strings are padded with zeroes at the
end.

### Header

| from | to   | content            |
|:-----|:-----|:-------------------|
| 0x00 | 0x04 | identifier: “BLoC” |
| 0x04 | 0x06 | number of entries  |
| 0x06 | 0x?? | entries            |
| 0x?? | 0x?? | structure          |

### Entry

| from | to   | content                    |
|:-----|:-----|:---------------------------|
| 0x00 | 0x?? | bit-encoded BLC expression |

### Structure

This reflects the basic structure of the program and can’t use
variables. Instead, the structure entry uses the following derivation of
normal bit-encoded BLC:

| prefix | content                       |
|:-------|:------------------------------|
| 00M    | abstraction of expression `M` |
| 01MN   | application of `M` and `N`    |
| 1I     | 2 byte index to an entry      |

## Example

Let `E` be some kind of expression like `E=\x.(((M (\y.N)) M) N)`, where
`M` and `N` are both arbitrary expressions of length 16.

The raw BLC expression of `E` would then be `E=00010101M00NMN`. This
obviously has the drawback of redundant repetition of `M` and `N`.

A possible encoding in BLoC:

| from | to   | content                                                                    |
|:-----|:-----|:---------------------------------------------------------------------------|
| 0x00 | 0x04 | “BLoC”                                                                     |
| 0x04 | 0x06 | number of entries: 2                                                       |
| 0x06 | 0x16 | `M` in BLC                                                                 |
| 0x16 | 0x26 | `N` in BLC                                                                 |
| 0x26 | 0x32 | `000101011<M>001<N>1<M>1<N>`, where `<M>=0` and `<N>=1` are 2 byte indices |

Even in this small example BLoC uses less space than BLC (0x32 vs. 0x42
bytes).