Import the Num Crate

Rust is designed to be very lightweight and provides very little right out of the box.

Within the ecosystem, many functions and features which you might expect to be included into Rust std or core are actually delegated to small, well-known, and widely used crates.

For our next step, we want to access traits for basic numerical operations like:

  • CheckedAdd - A type which supports checked_add
  • CheckedSub - A type which supports checked_sub
  • Zero - A type which can return the value zero when calling zero()
  • One - A type which can return the value one when calling one()

To access these traits, we will need to import a new crate into our project.

Cargo.toml

When we first initialized our project, a Cargo.toml file was generated for us.

As mentioned before, it is very similar to a package.json file you would expect to find in a Node.js project.

Already in your Cargo.toml is metadata like the name of your project, the version of the crate you are building, and the edition of Rust you are using.

What you can see is that you can also add dependencies to your crate which will allow you to use other external crates and libraries in your project.

You can add the dependency by hand by editing your Cargo.toml file or you can run cargo add num.

Crates.io

Where is this crate coming from?

The Rust community has a large registry of available crates on crates.io. When you import a crate, it will use crates.io by default.

You can also import crates directly from github by specifying the repo where the source code can be found.

That would look something like:

[dependencies]
pallet-balances = { version = "4.0.0-dev", default-features = false, git = "https://github.com/paritytech/substrate.git", branch = "polkadot-v1.0.0" }

Add the Num Crate to Your Project

This step is short and simple.

Run cargo add num in your project directory and make sure your project compiles afterward.

You should see something like:

➜  rust-state-machine git:(master) ✗ cargo add num
    Updating crates.io index
      Adding num v0.4.1 to dependencies.
             Features:
             + std
             - alloc
             - libm
             - num-bigint
             - rand
             - serde
    Updating crates.io index
➜  rust-state-machine git:(master) ✗ cargo run
    Finished dev [unoptimized + debuginfo] target(s) in 0.01s
     Running `target/debug/rust-state-machine`

[package]
name = "rust-state-machine"
version = "0.1.0"
edition = "2021"

# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html

[dependencies]
num = "0.4.1"

diff --git a/Cargo.lock b/Cargo.lock
index 75fe297f..10ded84b 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -2,6 +2,91 @@
 # It is not intended for manual editing.
 version = 3
 
+[[package]]
+name = "autocfg"
+version = "1.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d468802bab17cbc0cc575e9b053f41e72aa36bfa6b7f55e3529ffa43161b97fa"
+
+[[package]]
+name = "num"
+version = "0.4.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b05180d69e3da0e530ba2a1dae5110317e49e3b7f3d41be227dc5f92e49ee7af"
+dependencies = [
+ "num-bigint",
+ "num-complex",
+ "num-integer",
+ "num-iter",
+ "num-rational",
+ "num-traits",
+]
+
+[[package]]
+name = "num-bigint"
+version = "0.4.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "608e7659b5c3d7cba262d894801b9ec9d00de989e8a82bd4bef91d08da45cdc0"
+dependencies = [
+ "autocfg",
+ "num-integer",
+ "num-traits",
+]
+
+[[package]]
+name = "num-complex"
+version = "0.4.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1ba157ca0885411de85d6ca030ba7e2a83a28636056c7c699b07c8b6f7383214"
+dependencies = [
+ "num-traits",
+]
+
+[[package]]
+name = "num-integer"
+version = "0.1.45"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "225d3389fb3509a24c93f5c29eb6bde2586b98d9f016636dff58d7c6f7569cd9"
+dependencies = [
+ "autocfg",
+ "num-traits",
+]
+
+[[package]]
+name = "num-iter"
+version = "0.1.43"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7d03e6c028c5dc5cac6e2dec0efda81fc887605bb3d884578bb6d6bf7514e252"
+dependencies = [
+ "autocfg",
+ "num-integer",
+ "num-traits",
+]
+
+[[package]]
+name = "num-rational"
+version = "0.4.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "0638a1c9d0a3c0914158145bc76cff373a75a627e6ecbfb71cbe6f453a5a19b0"
+dependencies = [
+ "autocfg",
+ "num-bigint",
+ "num-integer",
+ "num-traits",
+]
+
+[[package]]
+name = "num-traits"
+version = "0.2.17"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "39e3200413f237f41ab11ad6d161bc7239c84dcb631773ccd7de3dfe4b5c267c"
+dependencies = [
+ "autocfg",
+]
+
 [[package]]
 name = "rust-state-machine"
 version = "0.1.0"
+dependencies = [
+ "num",
+]
diff --git a/Cargo.toml b/Cargo.toml
index c7fe36cd..42b80bf8 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -6,3 +6,4 @@ edition = "2021"
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
+num = "0.4.1"