14-445 from CMU

• Intro
• Lecture 1
  • C++ Primer
    • std::string_view
    • trailing return types (fun -> type)
    • std::dynamic_cast
    • explicit constructors
    • virtual functions
    • why we can’t use the copy constructor
    • pseudocode

Intro

Author of learnaifromscratch swears that this course teaches you everything you need to know to get a job in OLAP. I’ll do it to learn about sql and how databases work internally. I don’t know modern c++ (did a course in c++ that was more like in college but that’s about it), so I’ll pick that up too as I go.

Lecture 1

C++ Primer

Project requires us to implement a copy-on-write trie (operations return new tries, instead of modifying by reference) by completing the implementation. This is really a test for your c++ abilities. I don’t have any so I’ll be picking everything up and writing about what I learn here as I go through it.

std::string_view

• immutable read-only view(reference) to a string; use this when you don’t need to modify the string, but only to access it

trailing return types (fun -> type)

• this allows infering types using auto, for example, in:

template <class T>
auto Trie::Get(std::string_view key) const -> const T *
{
}

• chatgpt says that this is only a matter of style, so it’s equivalent to

template <class T>
const T* Trie::Get(std::string_view key) const
{
}

i guess it’s more readable? not sure

std::dynamic_cast

explicit constructors

• using explicit in the constructor means that it won’t be usable for implicit type converstion; so you’ll only be able to initialize the object using the constructor, instead of also allowing to initialize it with assignment

virtual functions

• same concept as in OOP, allows a function to be overriden but this happens at runtime instead of compile time

why we can’t use the copy constructor

• not really sure?

pseudocode

• Trie.Put(key: str, value: any) for i in len(key): char = key[i] if not char in children: create children node with char as key val = str(value[i]) children[char] = val

• Trie.Get(key) val = "" for i in len(key): char = key[i] val += children[char]

  return val