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+# num-bigint
+
+[![crate](https://img.shields.io/crates/v/num-bigint.svg)](https://crates.io/crates/num-bigint)
+[![documentation](https://docs.rs/num-bigint/badge.svg)](https://docs.rs/num-bigint)
+![minimum rustc 1.15](https://img.shields.io/badge/rustc-1.15+-red.svg)
+[![Travis status](https://travis-ci.org/rust-num/num-bigint.svg?branch=master)](https://travis-ci.org/rust-num/num-bigint)
+
+Big integer types for Rust, `BigInt` and `BigUint`.
+
+## Usage
+
+Add this to your `Cargo.toml`:
+
+```toml
+[dependencies]
+num-bigint = "0.2"
+```
+
+and this to your crate root:
+
+```rust
+extern crate num_bigint;
+```
+
+## Features
+
+The `std` crate feature is mandatory and enabled by default.  If you depend on
+`num-bigint` with `default-features = false`, you must manually enable the
+`std` feature yourself.  In the future, we hope to support `#![no_std]` with
+the `alloc` crate when `std` is not enabled.
+
+Implementations for `i128` and `u128` are only available with Rust 1.26 and
+later.  The build script automatically detects this, but you can make it
+mandatory by enabling the `i128` crate feature.
+
+## Releases
+
+Release notes are available in [RELEASES.md](RELEASES.md).
+
+## Compatibility
+
+The `num-bigint` crate is tested for rustc 1.15 and greater.
+
+## Alternatives
+
+While `num-bigint` strives for good performance in pure Rust code, other
+crates may offer better performance with different trade-offs.  The following
+table offers a brief comparison to a few alternatives.
+
+| Crate            | License        | Min rustc | Implementation |
+| :--------------- | :------------- | :-------- | :------------- |
+| **`num-bigint`** | MIT/Apache-2.0 | 1.15      | pure rust |
+| [`ramp`]         | Apache-2.0     | nightly   | rust and inline assembly |
+| [`rug`]          | LGPL-3.0+      | 1.31      | bundles [GMP] via [`gmp-mpfr-sys`] |
+| [`rust-gmp`]     | MIT            | stable?   | links to [GMP] |
+| [`apint`]        | MIT/Apache-2.0 | 1.26      | pure rust (unfinished) |
+
+[GMP]: https://gmplib.org/
+[`gmp-mpfr-sys`]: https://crates.io/crates/gmp-mpfr-sys
+[`rug`]: https://crates.io/crates/rug
+[`rust-gmp`]: https://crates.io/crates/rust-gmp
+[`ramp`]: https://crates.io/crates/ramp
+[`apint`]: https://crates.io/crates/apint