This is a pet-project interpreter which implements a random access machine as described by Cook and Reckhow.
divarema
only implements the machine's basic instructions; the paper
linked above also includes a proof regarding a VM built with these
instructions which can execute arbitrary programs stored in main
memory within some time bounds (so an arbitrarily large program can be
executed with a space-bounded instruction and ROM program).
This is a pet project to help me learn about models of computation and about Rust (hence didactic and vanity). It's not intended for any other application, but if you get something from it that's great :)
divarema
reads instructions form a file and executes them. The
machine has eight instructions and two kinds of memory. Program memory
stores the program being executed and is immutable. Main memory is
available to the program and consists of a number (by default, 8) of
mutable registers that can hold signed 32-bit integers. Main memory is
indexed by integers, starting from 0.
Two special registers control operation and implement arithmetic:
- The accumulator
ACC
is the target and source of arithmetic and copy operations - The instruction counter
IC
holds the address (in program-memory) of the next instruction to execute, manipulated by control-flow operations
Programs for divarema
can include the following instructions:
Operation | Description | Mnemonic |
---|---|---|
LOAD j | ACC <- j ; IC <- IC+2 | load |
ADD j | ACC <- [ACC] + [Xj] ; IC <- IC+2 | add |
SUB j | ACC <- [ACC] - [Xj] ; IC <- IC+2 | subtract |
STORE j | Xj <- [ACC] ; IC <- IC+2 | store |
JGZ j | if AC > 0 then IC <- j else IC <- IC+2 | jump-greather-than-zero |
READ j | Xj <- next input | read |
PRINT j | output [Xj] | |
HALT _ | stop execution | halt |
This software is licensed under the GNU General Public License
v3.0. See LICENSE
or license's website
for details.