Add [Package and Crate]

ChangeLog.md

@@ -1,5 +1,9 @@
 # ChangeLog
 
+### 2022-03-14
+
+- Add [Package and Crate](https://practice.rs/crate-module/crate.html)
+
 ### 2022-03-11
 
 - Add one exercise in [Patterns](https://practice.rs/pattern-match/patterns.html)

src/SUMMARY.md

@@ -1,6 +1,6 @@
 # Summary
 
-- [Rust By Practice](about.md)
+- [Rust By Practice](why-exercise.md)
 - [Variables](variables.md)
 - [Basic Types](basic-types/intro.md)
   - [Numbers](basic-types/numbers.md)
@@ -39,8 +39,8 @@
 - [Result and panic](result-panic/intro.md)
   - [panic!](result-panic/panic.md)
   - [Result and ?](result-panic/result.md)
-- [Crate and module TODO](crate-module/intro.md)
+- [Crate and module](crate-module/intro.md)
-  - [Crate](crate-module/crate.md)
+  - [Package and Crate](crate-module/crate.md)
   - [Module](crate-module/module.md)
   - [use and pub](crate-module/use-pub.md)
 - [Comments and Docs TODO](comments-docs.md)

src/crate-module/crate.md

@@ -1 +1,106 @@
-# Crate
+# Package and Crate
+A package is a project which you create with Cargo (most cases), so it contains a `Cargo.toml` file in it.
+
+1. 🌟 Create a package  with below layout:
+```shell
+.
+├── Cargo.toml
+└── src
+    └── main.rs
+
+1 directory, 2 files
+```
+
+```toml
+# in Cargo.toml
+[package]
+name = "hello-package"
+version = "0.1.0"
+edition = "2021"
+```
+
+> Note! We will this package across the whole chapter
+
+2. 🌟 Create a package with below layout:
+```shell
+.
+├── Cargo.toml
+└── src
+    └── lib.rs
+
+1 directory, 2 files
+```
+
+```toml
+# in Cargo.toml
+[package]
+name = "hello-package1"
+version = "0.1.0"
+edition = "2021"
+```
+
+> Note! This package could be safely removed due to the first one's existence.
+
+3. 🌟 
+```rust
+/* FILL in the blank with your ANSWER */
+
+// Q: Whats the difference between package 1# and 2# ?
+// A: __
+```
+
+
+## Crate
+A crate is a binary or library. The crate root is a source file that the Rust compiler starts from and makes up the root module of the crate.
+
+In package `hello-package`, there is binary crate with the same name as the package : `hello-package`, and `src/main.rs` is the crate root of this binary crate.
+
+Similar to `hello-package`, `hello-package1` also has a crate in it, however, this package doesn't contain a binary crate but a library crate, and `src/lib.rs` is the crate root.
+
+4. 🌟
+```rust
+/* FILL in the blank with your ANSWER */
+
+// Q: Whats the name of the library crate in package `hello-package1`?
+// A: __
+```
+
+
+5. 🌟🌟 Add a library crate for `hello-package` and describe it's files tree below:
+```shell
+# FILL in the blanks
+.
+├── Cargo.lock
+├── Cargo.toml
+├── src
+│   ├── __
+│   └── __
+```
+
+After this step, there should be two crates in package `hello-package`: **a binary crate and a library crate, both with the same name as the package**.
+
+6. 🌟🌟🌟 A package can contain at most one library crate, but it can contain as many binary crates as you would like by placing files in `src/bin` directory: **each file will be a separate binary crate with the same name as the file**.
+
+```shell
+# Create a package which contains 
+# 1. three binary crates: `hello-package`, `main1` and `main2`
+# 2. one library crate
+# describe the directory tree below
+.
+├── Cargo.toml
+├── Cargo.lock
+├── src
+│   ├── 
+│   ├── 
+│   └── 
+│       └── 
+│       └── 
+├── tests # directory for integrated tests files
+│   └── some_integration_tests.rs
+├── benches # dir for benchmark files
+│   └── simple_bench.rs
+└── examples # dir for example files
+    └── simple_example.rs
+```
+
+Yep, as you can see, the above package structure is very standard and is widely used in many Rust projects.

src/crate-module/intro.md

@@ -1 +1,5 @@
 # Crate and module
+Learning resources: 
+- English: [Rust Book Chapter 7](https://doc.rust-lang.org/book/ch07-00-managing-growing-projects-with-packages-crates-and-modules.html)
+- 简体中文: [Rust语言圣经 - 包和模块](https://course.rs/basic/crate-module/intro.html)
+