Add to chapter 8

compiler/chapter_2.md

@@ -405,7 +405,7 @@ while (token !== null) {
 
 ## Exercises
 
-1. Implement the operators: `-`, `*`, `/`, `(`, `)`, `.`, `,`, `;`, `[`, `]`, `!=`, `<`, `>`, `<=` and `>=`.
+1. Implement the operators: `-`, `*`, `/`, `(`, `)`, `.`, `,`, `:`, `;`, `[`, `]`, `!=`, `<`, `>`, `<=`, `>=` and `->`.
 2. Implement the keywords: `true`, `false`, `null`, `or`, `and`, `not`, `loop`, `break`, `let`, `fn` and `return`.
 3. \* Implement single line comments using `//` and multiline comments using `\*` and `*\` (\*\* extra points if multiline comments can be nested, eg. `/* ... /* ... */ ... */`).
 4. \* Reimplement integers such that integers are either `0` or start with `[1-9]`.

compiler/chapter_8.md

@@ -11,9 +11,30 @@ For a type checker to be able to determine all the types of all values, the prog
 
 We'll need explicit typing for the following types: null, int, string, bool, array, struct and function.
 
+We want to be able to specify types in let-statements and fn-statements, like the following.
+
+```rs
+let a: int = 5;
+
+fn add(a: int, b: int) -> int { /*...*/ }
 ```
+
+For array and function types, we also want to specify details like contained type, return type and parameter types, like the following.
+
+```rs
+let op: fn(int, int) -> int = add;
+
+let values: [int] = array();
 ```
 
+
+
+### Parsing parameters
+
+Both function definitions and let-statements use parameters.
+
+### Parsing functions
+
 ## Types in AST
 
 ```ts