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# RAMP - Rust Arithmetic in Multiple Precision

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

```
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.