first bit of guessing game ch2

guessing_game/Cargo.toml

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+[package]
+name = "guessing_game"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]

guessing_game/src/main.rs

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+// some things are automatically loaded in every rust program
+// https://doc.rust-lang.org/std/prelude/index.html
+// for extras, import them with `use`:
+use std::io;
+
+fn main() {
+    println!("Guess the number!");
+    println!("input your guess");
+    // vars are immutable by default, change this
+    // The :: syntax in the ::new line indicates that new is an _associated function_ of the String
+    //         a function that’s implemented on a type
+    let mut guess = String::new();
+    // could still call this without importing it via std::io::stdin
+    // this can be one line, it is broken up for readability.
+    io::stdin()
+        // & indicates that this argument is a reference,
+        // references are also immutable by default so &mut is needed
+        .read_line(&mut guess)
+        // expect handles the Err variant by crashing the program. There are other ways to handle
+        // errors.
+        .expect("Failed to read line");
+    // read_line returns a `result` value. result is an enum. Each possible state is a variant.
+    // Result's variants are Ok and Err
+
+    println!("you guessed: {guess}");
+}