First examples from rust book

+**/target
+**/*.rs.bk
 **/.cargo/*

+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+[[package]]
+name = "branches"
+version = "0.1.0"
+

+[package]
+name = "branches"
+version = "0.1.0"
+authors = ["Georg Hopp <georg@steffers.org>"]
+edition = "2018"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]

+//
+// Control Flow Examples
+//
+// Georg Hopp <georg@steffers.org>
+//
+// Copyright © 2019 Georg Hopp
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+//
+
+fn main() {
+    let condition = true;
+    let number = if condition {
+        5
+    } else {
+        6
+    };
+
+    println!("The value of number is: {}", number);
+}

+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+[[package]]
+name = "functions"
+version = "0.1.0"
+

+[package]
+name = "functions"
+version = "0.1.0"
+authors = ["Georg Hopp <georg@steffers.org>"]
+edition = "2018"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]

+fn main() {
+    another_function(5, add_five(6));
+}
+
+fn another_function(x: i32, y: i32) {
+    println!("The value of x id: {}", x);
+    println!("The value of y id: {}", y);
+}
+
+fn add_five(x: i32) -> i32 {
+    x + 5
+}

-/target
-**/*.rs.bk

-/target
-**/*.rs.bk

+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+[[package]]
+name = "loops"
+version = "0.1.0"
+

+[package]
+name = "loops"
+version = "0.1.0"
+authors = ["Georg Hopp <georg@steffers.org>"]
+edition = "2018"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]

+//
+// Loops examples.
+//
+// Georg Hopp <georg@steffers.org>
+//
+// Copyright © 2019 Georg Hopp
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+//
+
+fn main() {
+    // It seams that to use loops this way you absolutely need a mutable.
+    // If I build it with a normal type and try to shadow it within the loop
+    // the outer variable is always used as input for the shadow, thus it is
+    // always the same.... that really sucks.
+    let mut counter = 0;
+
+    let result = loop {
+        counter = counter + 1;
+        if counter == 10 {
+            break counter * 2;
+        }
+    };
+
+    println!("The result is {}", result);
+
+    // The same is true with «while» ... which again sucks.
+    let mut number = 3;
+
+    while number != 0 {
+        println!("{}!", number);
+        number = number - 1;
+    }
+
+    println!("LIFTOFF!!!");
+
+    // apart from beeing frustrated about the above facts... lets continue.
+    let a = [10, 20, 30, 40, 50];
+    let mut index = 0;
+
+    while index < 5 {
+        println!("the value is: {}", a[index]);
+        index = index + 1;
+    }
+
+    for element in a.iter() {
+        println!("the value is still: {}", element);
+    }
+
+    for number in (1..4).rev() {
+        println!("for {}!", number);
+    }
+}

+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+[[package]]
+name = "ownership"
+version = "0.1.0"
+

+[package]
+name = "ownership"
+version = "0.1.0"
+authors = ["Georg Hopp <georg@steffers.org>"]
+edition = "2018"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]

+//
+// Examples related to ownership, also introducing String.
+//
+// Georg Hopp <georg@steffers.org>
+//
+// Copyright © 2019 Georg Hopp
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+//
+
+fn main() {
+    concat();
+    move_variable();
+    clone_variable();
+
+    let s = String::from("hello");  // s comes into scope
+
+    take_ownership(s);              // s's value moves into the function
+                                    // … and so is no longer valid here.
+    let x = 5;                      // x comes into scope
+
+    makes_copy(x);                  // the scalar value has the Copy trait and
+                                    // lives on the stack and thus is still
+                                    // valid here.
+
+    let _s1 = gives_ownership();     // move the return value into _s1
+    let  s2 = String::from("hello"); // s2 comes into scope
+    let _s3 = takes_and_gives(s2);   // s2 is moved into function, which in
+                                     // turn moves the return value into _s3.
+
+    let s1 = String::from("hello");  // s1 comes into scope.
+    let len = calculate_length(&s1); // A reference to s1 is given to a
+                                     // calculate_length which effectively is
+                                     // not s1 itself but another pointer to
+                                     // s1… which is the reason that we still
+                                     // can use it below.
+    let _another_s = &s1;            // again only a reference which does not
+                                     // take ownership, thus s1 can still be
+                                     // used below.
+    println!("The length of '{}' is {}.", s1, len);
+
+    // Passing values as reference to a function is called borrowing. A
+    // borrowed value can't be changed.
+    change(&s1);
+
+    // but we can force this… which is probably not the best of ideas most
+    // of the time…
+    let mut s_mut = String::from("hello");
+    change_mutable(&mut s_mut);
+
+    // but you can have only one mutable reference of a value in a single
+    // scope. The following would fail with:
+    // cannot borrow `s_mut` as mutable more than once at a time second
+    // mutable borrow occurs here
+    // let r1 = &mut s_mut;
+    // let r2 = &mut s_mut;
+    // println!("{}, {}", r1, r2);
+
+    // We also can't have an immutable reference while we have a mutable one.
+    // Look on Page 98 for an explanation.
+
+    // The scope of references is not the whole block they are introduced in
+    // but goes only until their last usage. Thus if you first have an
+    // immutable reference but never use it after a mutable reference is
+    // declared, that would be ok… At all this is kind of confusing and very
+    // Mozzilaish. :D
+
+    // Now we demonstrate string slices…
+    let s4 = String::from("hello world");
+    let s_slice = first_word(&s4);
+
+    // working with an mutable reference like with s4.clear() will not
+    // compile at this point because we already have and use later on an
+    // immutable reference.
+
+    println!("The slice was: {}", s_slice);
+
+    // not that string literals are slices. They are immutable references of
+    // the programs TEXT segment. Thats the reason why they are immutable.
+
+    // Thus try generic_first_word…
+    println!("First word on literal: {}", generic_first_word("hello world"));
+    println!("First word on String: {}", generic_first_word(&s4[..]));
+} // x and s go out of scope but nothing happens for s because this function
+  // has no longer the ownership of s.
+  // s3 goes out of scope and is dropped. s2 was moved and s1 is dropped.
+
+fn concat() {
+    let mut s = String::from("hello");
+    s.push_str(", world!");
+    println!("{}", s);
+}
+
+fn move_variable() {
+    let s1 = String::from("hello");
+    let s2 = s1; // does not copy data but only the String structure.
+    // when using s1 below we get an error that a moved value was borrowed.
+    println!("{}, world!", s2);
+}
+
+fn clone_variable() {
+    let s1 = String::from("hello");
+    let s2 = s1.clone();
+    // this time both are valid.
+    println!("s1 = {}, s2 = {}", s1, s2)
+}
+
+fn take_ownership(some_string: String) { // some_string comes into scope
+    println!("{}", some_string);
+} // some_string goes out of scope and «drop» is called, thus memory freed.
+
+fn makes_copy(some_integer: i32) { // some integer comes into scope
+    println!("{}", some_integer);
+} // Here, some_integer goes out of scope but because it was a copy and on the
+  // stack nothing special happens… beside that stack space is freed.
+
+fn gives_ownership() -> String { // this will move the return value into the
+                                 // calling function.
+    let some_string = String::from("hello"); // some_string comes into scope
+    some_string
+}
+
+fn takes_and_gives(a_string: String) -> String { // a_string comes into scope
+    a_string                                     // and is returned and moved
+                                                 // to the calling function.
+} // a_string goes out of scope but nothing happens as it is moved.
+
+fn calculate_length(s: &String) -> usize { // s comes into scope. It is a
+                                           // reference. References do not
+                                           // take ownership of the underlying
+                                           // value which is the String in
+                                           // main.
+    s.len()
+} // Here s goes out of scope but because it has no ownership of the String
+  // nothing happens.
+
+fn change(_some_string: &String) {
+    // the following would give this error:
+    // `_some_string` is a `&` reference, so the data it refers to cannot be
+    // borrowed as mutable
+    // _some_string.push_str(", world!");
+}
+
+fn change_mutable(some_string: &mut String) {
+    some_string.push_str(", world");
+}
+
+fn first_word(s: &String) -> &str {
+    let bytes = s.as_bytes();
+
+    for (i, &item) in bytes.iter().enumerate() {
+        if item == b' ' {
+            return &s[..i];
+        }
+    }
+
+    &s[..]
+}
+
+// To make first_word work on either string literals (which are in fact string
+// slices, s.o.) one would write first_word like this…
+fn generic_first_word(s: &str) -> &str {
+    let bytes = s.as_bytes();
+
+    for (i, &item) in bytes.iter().enumerate() {
+        if item == b' ' {
+            return &s[..i];
+        }
+    }
+
+    &s[..]
+}

+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+[[package]]
+name = "variables"
+version = "0.1.0"
+

+[package]
+name = "variables"
+version = "0.1.0"
+authors = ["Georg Hopp <georg@steffers.org>"]
+edition = "2018"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]

+fn main() {
+    let mut x = 5;
+    println!("The value of x is: {}", x);
+    x = 6;
+    println!("The value of x is: {}", x);
+}