06_Modules.ipynb

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    "# Rust Modules\n",
    "- Modules are defined by mod keyword\n",
    "- By default everything inside a module `a` will be private to `a`, its sibling and its parent, the entities inside `a` can only be accessed by the other entities that are inside `a`.\n",
    "- Modules can contain other modules inside them.\n",
    "- Modules can also contain any other valid rust code inside them.\n",
    "- Every module has a module called `crate` as its top.\n",
    "- Every module can be accesed by either its absolute path tha starts with crate or relative path."
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   "source": [
    "## `pub` keyword\n",
    "Any entity can be made public to its parent and parents sibling elements by adding `pub` keyword to it."
   ]
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    "mod front_of_house {\n",
    "    pub mod hosting {\n",
    "        pub fn add_to_waitlist(){\n",
    "            println!(\"added to waitlist\");\n",
    "        }\n",
    "        pub fn serve_order(){\n",
    "            println!(\"order served\");\n",
    "        }\n",
    "    }\n",
    "}"
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      "added to waitlist\n",
      "added to waitlist\n"
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   "source": [
    "// accessing with absolute path\n",
    "crate::front_of_house::hosting::add_to_waitlist();\n",
    "//accessing with relative path\n",
    "front_of_house::hosting::add_to_waitlist();"
   ]
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   "source": [
    "## `super` keyword\n",
    "We can access entities that are relatively higher in the same module by using super keyword."
   ]
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     "text": [
      "cooking order\n",
      "order served\n"
     ]
    }
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   "source": [
    "// using super keyword\n",
    "mod back_of_house {\n",
    "     pub fn fix_incorrect_order(){\n",
    "         cook_order();\n",
    "         super::front_of_house::hosting::serve_order();\n",
    "     }\n",
    "     fn cook_order(){\n",
    "         println!(\"cooking order\");\n",
    "     }\n",
    "}\n",
    "\n",
    "back_of_house::fix_incorrect_order();"
   ]
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   "source": [
    "## `use` keyword"
   ]
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     "text": [
      "order served\n",
      "order served\n",
      "order served\n",
      "added to waitlist\n"
     ]
    }
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   "source": [
    "// bring hosting module into the scope\n",
    "use crate::front_of_house::hosting::{self, serve_order, add_to_waitlist};\n",
    "//use self::front_of_house::hosting;\n",
    "//use self::front_of_house::serve_order;\n",
    "\n",
    "front_of_house::hosting::serve_order();\n",
    "hosting::serve_order();\n",
    "serve_order();\n",
    "add_to_waitlist();"
   ]
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   "source": [
    "### `pub` keyword will be used with `use` keyword when we want to export our module (make our module accessible from other projects)."
   ]
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   "source": [
    "pub use crate::front_of_house::hosting;"
   ]
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   "source": [
    "## `as` keyword can be use to import any module or any other entity from a module into the scope with a diffrent name"
   ]
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   "source": [
    "use std::io::Result as IO_Result;"
   ]
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   "source": [
    "## The `glob` or `*` operator\n",
    "it is used to import all the entities into the scope that are within the given module."
   ]
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   "source": [
    "use std::io::*;"
   ]
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   "source": [
    "## Modules in Seperate Files\n",
    "\n",
    "- In the main lib.rs file, declare the front_of_house module but just declare.\n",
    "- The inner code will be in a file with same name in the same directory.\n",
    "- If you want to break it down further, extract the code of hosting module and put it in a dir that is named after the main module and put it in the file named hosting.\n",
    "- See the below example for clarity:\n",
    "\n",
    "./front_of_house/hosting.rs\n",
    "___\n",
    "```\n",
    "pub fn serve_drink(){\n",
    "    println!(\"drinks served\");\n",
    "}\n",
    "```\n",
    "\n",
    "\n",
    "./front_of_house.rs\n",
    "___\n",
    "```\n",
    "pub mod hosting;\n",
    "```\n",
    "./lib.rs\n",
    "___\n",
    "```\n",
    "mod front_of_house;\n",
    "use front_of_house::hosting;\n",
    "hosting::serve_drink();\n",
    "``` "
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