finished ch3 not ch4

functions_rust/Cargo.lock

@@ -0,0 +1,7 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 4
+
+[[package]]
+name = "functions_rust"
+version = "0.1.0"

functions_rust/src/main.rs

@@ -1,6 +1,7 @@
 fn main() {
     println!("Hello, world!");
     example_function(1, 4);     // can be delared before or after function that uses it
+    println!("From Return function: {}", with_return_plus_one(18));
 }
 
 // fn is the keyword for functions
@@ -11,5 +12,59 @@ fn example_function (x:i8, y:u16) {
 
     // can be used directly form pram delaration
     println!("Look anthoer Function {} {y}", x);
+    let a = {
+        let b = 3;
+        b + 1
+    };
+    println!("The value of a is: {a}");
+
 
 }
+
+// Statements do not return a value
+// Function def is a statement
+// Calling a function is not a statement
+// let is a statement, and cannot assign anything nor does it return anything unlike in C and Ruby
+// let x = (let y = 6);
+// STATEMENTS END WITH ;
+
+
+// Expressions evalulate and may return a non-unit value
+// let y = 6 is an expression that evalulates to 6, then writes to memory under the variable y
+// calling a function is an expression, math, and calling a macro are all expressions
+// adding a new scope block using {} is an expression
+//  ex let y = { // value bound to y in the statment let y is 6
+//      let x = 5;
+//      x + 1
+//     }
+
+//  EXPRESSIONS DO NOT END WITH ;
+// if you add a ; to the end of a statment it will turn into a statement and not return anything
+// unless it is a return keyword
+// or if it is a marco
+
+
+fn with_return_plus_one (c: i16) -> i16 {
+    // return 8; // can return early with return keyword
+    c + 1 // also allowed an a normal function
+    // c + 1; this is not an expression and will not return a value
+}
+
+// if you want to return a non-unit must decalre type after -> keyword
+// return value is the same as the final value is the same as the last line/expression in the function
+// can return early with the return keyword plus a value but it is implied by default
+// return type must match unit != i16 and thereforw will cause an error
+
+fn five () -> i32 {
+    5 // this is an expression
+}
+
+// also perfectally valid
+// can assign values from a expression/function return
+
+fn assign_five_fn () {
+    let d = five();
+}
+
+// comments annotate the code below it
+// no multiline comments