what is get(),find(),end(),raw() keywords in eos smart contract?

Question

how and when to useall these keywords and what they actually means? and what is the difference in these 2 statement given below

auto itr = loan_table.get(loan_id);
auto itr1 = loan_table.find(loan_id);

main code

void mainloan::checkperiod(uint64_t loan_id, uint64_t instl_check, uint64_t delay){
  require_auth(get_self());
  auto itr = loan_table.get(loan_id);
  auto itr1 = loan_table.find(loan_id);

  eosio::transaction t{};
  eosio::print("  second txn created.    ");
  t.actions.emplace_back(
      permission_level(get_self(), "active"_n),
      get_self(),
      "checkpayment"_n,
      std::make_tuple(loan_id, instl_check));
  eosio::print("  |||||action inserted in txn w delay set.   ");
 t.delay_sec = delay; //7 days=>1 installment  //30*24*60*60;   //delay in seconds => 1 month in sec
 eosio::print(" ||delay set.    ");
 t.send(now()+delay, get_self() /*, false */);
 eosio::print(" ||tnx sent.   ");

}

Answer 1

These are part of the EOS multi-index. Latest documentation: https://eosio.github.io/eosio.cdt/1.6.0/group__multiindex.html

get()

• Get takes 2 arguments, the key to search for, and the error message to return if the key is not found.
• https://eosio.github.io/eosio.cdt/1.6.0/group__multiindex.html#function-get

find()

• Unlike get, find only takes 1 argument, the key to search for. If they key is not find, it will return an end() iterator.
• https://eosio.github.io/eosio.cdt/1.6.0/group__multiindex.html#function-find

end()

• The end() function will return an iterator that can be decremented or compared against to see if the table is empty.
• https://eosio.github.io/eosio.cdt/1.6.0/group__multiindex.html#function-end

raw()

• The raw() is a class member of the fc library and is a serialization wrapper for uint64_t
• https://github.com/EOSIO/fc/blob/master/include/fc/io/raw.hpp