finished ch19 intro

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.obsidian/workspace.json

@@ -49,6 +49,20 @@
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     "Characteristics of OO Languages.md",
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@@ -230,7 +245,6 @@
     "The Performance Closures and Iterators.md",
     "Improving The IO Project.md",
     "Tests.md",
-    "The Preformance Closures and Iterators.md",
     "minigrep/src/lib.rs",
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Implementing OO Design Pattern.md

@@ -346,7 +346,7 @@ Then we call the `unwrap` method, we know this will never panic.
 
 We know the methods on `Post` ensure that `state` will always contain a `Some` value when those methods are done.
 
-This is a case where we have more information than the compiler (previously discussed in [Ch 9]()) when we know that a `None` value is never possible, even though the compiler isn't able to understand that.
+This is a case where we have more information than the compiler (previously discussed in [Ch 9](./Error%20Handling.md#cases-in-which-you-have-more-info-than-the-compiler)) when we know that a `None` value is never possible, even though the compiler isn't able to understand that.
 
 Now at this point, when we call `content` on the `&Box<dyn State>`, deref coercion will take effect on the `&` and the `Box` so the `content` method will ultimately be called on the type that implements the `State` trait.
 

Pattern Matching.md

@@ -1 +1,34 @@
 # Patterns and Matching
+*Patterns* are a special syntax in Rust for matching against the structure of types, both complex and simple.
+
+Using patterns in conjunction with `match` expressions and other constructs give you more control over a program's flow.
+
+A pattern consists of some combination of the following:
+- Literals
+- Destructured arrays, enums, structs, or tuples
+- Variables
+- Wildcards
+- Placeholders
+Some examples include `x`, `(a, 3)` and `Some(Color::Red)`.
+
+In the contexts in which patterns are valid, these components describe the shape of data.
+
+Our program then matches values against the patterns to determine whether it has the correct shape of data to continue running a particular piece of code.
+
+In order to use a pattern, we compare it to some value.
+
+If the pattern matches the value, we use the value parts in our code.
+
+Recall the `match` expression that used patterns, such as the coin-sorting machine example.
+
+If the value fits the shape of the pattern, we can use the named pieces.
+
+If it doesn't, the code associated with the pattern won't run.
+
+This chapter is intended to be a reference on all things related to patterns.
+
+We will cover:
+- Valid places to use patterns [Section Link Here]()
+- Difference between refutable and irrefutable patterns
+- different kinds of pattern syntax
+By the end you will know how to use patterns to express many concepts in a clear way.

Places Patterns Can Be Used.md

@@ -0,0 +1 @@
+# All the Places Patterns Can Be Used