# RAMP - Rust Arithmetic in Multiple Precision
[](https://travis-ci.org/Aatch/ramp)
[](https://crates.io/crates/ramp)
**[Documentation](https://aatch.github.io/ramp/ramp)**
Ramp is a high-performance mulitple-precision (aka "BigNum") library for working with numbers
bigger than can normally be handled. Usage is very easy, you can almost use them as regular
numbers.
## Example
```rust
extern crate framp as ramp;
use ramp::Int;
// Calculates n!
fn factorial(n: usize) -> Int {
let mut a = Int::from(1);
for i in 2..n {
a *= i;
}
return a * n;
}
```
As you can see, it is very easy to work with these numbers.
Operator overloads have been provided for by-value, which consumes the operand(s) and by-reference,
which does not. The by-value overloads will attempt to re-use the space for the result (this isn't
always possible).
Operator overloads have also been provided for `i32` and `usize`, allowing easy (and efficient)
operations when you have smaller numbers. The above example actually uses the `usize` overload,
meaning only one `Int` is ever allocated.
**NOTE** Due to use of unstable features (notably inline assembly), Ramp can only be compiled with
a nightly build of `rustc`.
## Why another library?
The `num` crate provides some bignum types that can be used, so why use Ramp? Well, Ramp is
specifically focussed on multiple-precision arithmetic, while `num` is a general-purpose numerics
library that happens to provide some multiple-precision arithmetic.
You should `num` if you aren't able to use unstable Rust features or just want a small amount of
functionality. Ramp should be used when you need high-performance and extra functionality.
## Overall Design
Ramp is split into two main parts: high-level code and low-level code. The high-level code is what
you should be using, however the low-level code is where the real work is done.
The low-level routines (in `ll`) are predominately unsafe functions that work with raw pointers,
and some of the routines are implemented using inline assembly to gain access to processor-specific
functionality.
### Limbs
The term "Limb" is used frequently in Ramp. It's a term borrowed from GMP and is a single "digit"
for the base that Ramp works in. Since the base is equal to 2^word_size, these are very large
"digits", hence the use of the word "Limb" instead.
## Future Work
Ramp is currently very rough and incomplete. Broadly, there are three types Ramp aims to provide:
integers, rationals, and floats. Integers (`Int`) are present and mostly complete, Rationals are
present and have a basic implementation. Floats are not yet implemented.
In the low-level routines, there are a few operations, notably multiplication and division, that
are currently implemented using the simplest working algorithm. While this is sufficient for
relatively small numbers, larger numbers should be using better algorithms.