autoperm is a tool for generating programs that apply stack effect diagrams. The produced result has the fewest number of MOV* instructions. The algorithm has it's foundations in Tarjan's Strongly Connected Components.
The library is backend agnostic. A brainfuck backend is provided. Installing the crate as a binary gives access to the autoperm command which uses this brainfuck backend.
* A MOV Clears the data at a particular memory address and writes it to a list of other cells
Eventually I will create a proper write up but for now here is my quick explanation.
test
cargo install autoperm
```bf $ autoperm a b -- b a [->+<]<[->+<]>>[-<<+>>]<
$ autoperm a b c -- c a b [->+<]<[->+<]<[->+<]>>>[-<<<+>>>]<
a -- a a a a [->>>>+<<<<]>>>>[-<+<+<+<+>>>>]<
a b c d -- d c a b [->+<]<<[->>+<<]>[-<+>]<<[->>+<<]>>>>[-<<<<+>>>>]<
a b c -- c <<[-]>[-]>[-<<+>>]<<
a b c d e f -- c d d f e e b <<<<<[-]>[->>>>>+<<<<<]>[-<<+>>]>[-<+<+>>]>>[-<<+>>]<[->>>+<<<]>>>[-<<+<+>>>]<
```
The program assumes the memory pointer is pointing at the top of the stack. Any new cells should start empty and there must be 1 free cell at the top of the stack for temporary storage.
For example: ```bf (a b c -- c) start must be: a b *c 0 // a and b are cleared <<[-]>[-]>[-<<+>>]<< end: *c 0 0 0
(a -- a a a a) start must be: a 0 0 0 0 // note: no 0s are initialized before usage [->>>>+<<<<]>>>>[-<+<+<+<+>>>>]< end: a a a *a 0 ```
A walk through for (a b -- a b a b)
```bf a b -- a b a b <[->>>>+<<<<]>>>>[-<<+<<+>>>>]<<<[->>>+<<<]>>>[-<+<<+>>>]<
0 *1 2 3 T a b 0 0 0
<[->>>>+<<<<] 0 → {T} *0 1 2 3 T 0 b 0 0 a
[-<<+<<+>>>>] T → {2 0} 0 1 2 3 *T a b a 0 0
<<<[->>>+<<<] 1 → {T} 0 *1 2 3 T a 0 a 0 b
[-<+<<+>>>] T → {1 3} 0 1 2 3 *T a b a b 0
< 0 1 2 *3 T a b a b 0 ```