C++17 in Detail: A Deep Dive Educative Quiz Answers

Get C++17 in Detail: A Deep Dive Educative Quiz Answers

C++ started in 1979 as an experiment, before being officially launched in 1983. In 1998, its first ISO standard was released. What started as an experimental language has quickly turned into a platform for solving complex problems that drive many industries: gaming, finance, data centres, vehicles, and even software for space missions, among many others. The latest release, C++17, builds upon the functionality of previous versions by further diversifying the power of C++ and increasing the language’s readability.

This course describes all the significant changes in C++17 and will give you the essential knowledge to stay at the edge of the latest features. What’s more, each section contains lots of practical examples and uses a bottom-up approach to give you a more comfortable start. If you have a moderate understanding of C++, this course is highly recommended as the next step in mastering the modern form of this language.

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Quiz 1: Language Clarification

Q1. In which order will the following expression be computed?

addInt(computeInt()).subtractFloat(computeFloat());

• addInt, computeInt, subtractFloat, computeFloat
• computeInt, subtractFloat, computeFloat, addInt
• computeInt, addInt, computeFloat ,subtractFloat
• computeFloat, subtractFloat, computeInt, addInt

Q2. Copy Elision is a popular optimisation that avoids creating unnecessary temporary objects.

• True
• False

Q3. Which of the following defines prvalue(pure rvalue)?

• An object that we can move from, which we can reuse. Usually, its lifetime ends soon
• An expression that has an identity, and which we can take the address of
• An expression whose evaluation computes the location of an object, bit-field, or function
• Something without a name, which we cannot take the address of, we can move from such expression

Quiz 2: Templates

Q1. What statement can not be used to deduce parameters Template?

• Option 1

std::tuple t(1, 2, 3); 

• Option 2

std::tuple<int,int,int> t(1, 2, 3); 

• Option 3

std::tuple<char,char> t(a, b, c); 

• Option 4

std::tuple t(x,y,z);

Q2. Pick up the correct syntax (as per new updates) for using variable number of parameters in a function:

• Option 1

auto sum(args){..}

template<typename T1, typename... T>
auto sum(T1 s, T... ts) {
    return s + sum(ts...);
}

• Option 2

template<typename ...Args> sum(Args ...args){
    return (args + ...);
}

• Option 3

auto sum(args t1, t2, ..){..}

template<typename T1, typename... T>
auto sum(T1 s, T... ts) {
    return s + sum(s,.. ts...);
}

• Option 4

auto sum(){..}

template<typename T1, typename... T>
auto sum(T1 s, T... ts) {
    return s + sum();
}

Q3. The typename is allowed in C++ 17 rather than class name?

• true
• false

Quiz 3: General Language Features

Q1. Have a look at the codes below. Which code shows the new syntax for writing if statements in C++17?

• Option 1

if(var > 100; auto var = findValue()){...}

• Option 2

if(auto var = findValue(); var > 100){...}

• Option 3

int var = findValue();
if(var > 100){...}

Q2. constexpr Lambda functions are constant expressions themselves, but they can invoke methods which are not constexpr.

• True
• False

Q3. C++17 introduces a new way of writing nested namespaces. How can we rewrite the code below to fit C++17 standards?

namespace Building {
  namespace Floor {
    namespace Room {
      ...
    }
  }
}

• Option 1

namespace Building::namespace Floor::namespace Room {
  ...
}

• Option 2

namespace Room::Floor::Building {
  ...
}

• Option 3

namespace Building {
  Floor {
    Room {
      ...
    }
  }
}

• Option 4

namespace Building::Floor::Room {
  ...
}

Quiz 4: Standard Attributes

Q1. Which of the following is NOT true about an Attribute?

• Is additional information that can be used by the compiler to produce code
• Might be utilised for optimisation
• Might be used for some specific code generation
• Allows you to write less expressive syntax

Q2. A [[fallthrough]] attribute suppresses compiler warnings about unused entities when they are declared with [[maybe_- unused]]

• True
• False

Q3. To suppress a warning you can explicitly cast the return value of a function to

• int
• string
• void
• float

Quiz 5: std::optional

Q1. For an optional variable var, which one of these methods of accessing its value is incorrect?

• Option 1

*var

• Option 2

var.value_or(10)

• Option 3

&var

Q2. An std::optional variable requires more memory than a normal data type variable.

• True
• False

Q3. Consider a custom class called myClass. What is the problem with calling the default constructor with an optional wrapper like this:

std::optional<myClass> var{myClass};

• It takes extra memory as a new temporary object is also created.
• The null type needs to be defined for custom classes so that optional knows what the empty object looks like.
• std::optional works for constructors with arguments, not the empty constructor

Quiz 6: std::variant

Q1. Which of the following is NOT a possible use of std::variant?

• Error handling
• Finite State Machines
• As a possible replacement for const std::string& parameter
• Polymorphism without vtables and inheritance

Q2. A visitor is “a Callable that accepts only a single possible alternative from every variant“.

• True
• False

Q3. In the code below why is monostate used?

std::variant<std::monostate, NotSimple, int> okInit;

• Allows you to create more complex types and pass more parameters
• Specify which type you want to change/set
• Used to specify which index you want to change/set
• Can be used with variants to represent an empty state

Q4. std::visit allows you not only to visit one variant but many in the same call.

• True
• False

Quiz 7: std::string_view

Q1. Which of these codes is not the correct way to create a string_view?

• Option 1

const char* myStr = "A String";
std::string_view sv { myStr };

• Option 2

std::string_view sv;
sv = {"A", " ", "String"};

• Option 3

std::string myStr = "Hello String";
std::string_view sv = myStr;

• Option 4

const char* myStr = "A String";
std::string_view sv { myStr, 3 };

Q2. What will be following code output?

  std::string myStr = "This is a string"; 
  std::string_view sv = myStr;
  auto sv2 = sv.substr(5, 4);
  std::cout << sv2.data(); 

• is a string
• This is a string
• is a
• out_of_range

Q3. The lifetime of a string_view must never exceed the lifetime of the string-owning object.

• True
• False

Quiz 8: String Conversions

Q1. from_chars is a set of overloaded functions: for integral types and floating point types

• True
• False

Q2. What is the purpose of std::chars_format fmt in the code below?

std::to_chars_result to_chars(char* first, char* last,
FLOAT_TYPE value,
std::chars_format fmt);

• Is a set of overloaded functions for integral and floating point types.
• Allows to specify precision
• Let’s you specify the output format
• Holds valuable information about the conversion process

Quiz 9: Parallel STL Algorithms

Q1. What is a parallel_unsequenced_policy?

• Execution policy type used to indicate that a parallel algorithm’s execution may be parallelized.
• Execution policy type used to indicate that a parallel algorithm’s execution may be parallelized and vectorized
• Execution policy type used to indicate that a parallel algorithm’s execution may not be parallelized

Q2. Which of the following is NOT true about the reduce algorithm?

• Returns the sum of all the elements in a range
• Applies a function object to the first n elements of a sequence
• Is a sequential algorithm
• Similar to std::partial_sum, includes the i-th input element in the i-th sum

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