ProgramGuru

Choose a Short Value

Choose a Short Value

The conditional operator selects one expression’s value.

A short pass label can be assigned in one expression when the two choices remain easy to read.

Before this lesson, review Select a Labeled Case when needed.

What you’ll learn

  • Use conditional operator to choose a Short Value.
  • Explain how the complete example produces Pass.
  • Make the practice change and explain why the result changes or stays the same.

Follow a complete C++ example

A short pass label can be assigned in one expression when the two choices remain easy to read.

Read the declarations above main before tracing its statements. Each declared name supplies the value, type or operation used later. The std:: prefix selects a name from the standard library, and cout << sends a value to the output stream.

C++17 · main.cpp · complete program

#include <iostream>
#include <string>

int main()  {
  int marks = 72;
  std::string label = marks >= 50 ? "Pass" : "Practise";
  std::cout << label << '\n';
  return 0;
}

Expected output

Pass
Run in C++ compiler →

Connect the code to its result

C++17 · source used in this explanation

#include <iostream>
#include <string>

int main()  {
  int marks = 72;
  std::string label = marks >= 50 ? "Pass" : "Practise";
  std::cout << label << '\n';
  return 0;
}

Expected output

Pass

The conditional operator selects one expression’s value. A short pass label can be assigned in one expression when the two choices remain easy to read.

Trace the result: Read the complete program below from its starting values to the output operations. Each std::cout statement displays the value supplied at that point; \n begins the next line. The resulting lines, in order, are Pass. In this example, distinguish what the program calculates or changes from what it actually displays.

Important mistakes and boundaries

Only the selected expression is evaluated. Complex nested choices usually deserve an if-else statement.

Change the school example

C++17 · edit this complete example

#include <iostream>
#include <string>

int main()  {
  int marks = 72;
  std::string label = marks >= 50 ? "Pass" : "Practise";
  std::cout << label << '\n';
  return 0;
}

Your task: Set marks to 40. Before running your edited program, predict the new output and explain which stored value, condition or object changes. Keep the rest of the example intact.

Use the complete source repeated here; this task does not depend on remembering code from another section.

Worked answer and reasoning

Worked variation: Set marks to 40. The chosen label is Practise.

The conditional operator selects one expression’s value. A short pass label can be assigned in one expression when the two choices remain easy to read.

Only the selected expression is evaluated. Complex nested choices usually deserve an if-else statement.

For a baseline run, save this source as main.cpp and use clang++ -std=c++17 -Wall -Wextra -pedantic main.cpp -o school, or equivalent g++ flags. Recompile after editing so that you run the updated executable.

The source and output below belong to the edited program. Compare them with the original example to see the consequence of this single change.

C++17 · worked variation · complete program

#include <iostream>
#include <string>

int main()  {
  int marks = 40;
  std::string label = marks >= 50 ? "Pass" : "Practise";
  std::cout << label << '\n';
  return 0;
}

Expected output

Practise
Run in C++ compiler →

Check your understanding

C++17 · original program for this question

#include <iostream>
#include <string>

int main()  {
  int marks = 72;
  std::string label = marks >= 50 ? "Pass" : "Practise";
  std::cout << label << '\n';
  return 0;
}
Before making the practice edit, what does the original C++17 program print?
Choose one answer. You can try again.

Answer and explanation

Pass

The conditional operator selects one expression’s value. A short pass label can be assigned in one expression when the two choices remain easy to read. Only the selected expression is evaluated. Complex nested choices usually deserve an if-else statement.

What to remember

The conditional operator selects one expression’s value. Only the selected expression is evaluated. Complex nested choices usually deserve an if-else statement.

Useful connections: Select a Labeled Case, Give a Task a Name.

Language and design guidance: C++ Core Guidelines and C++ working draft. The draft describes an evolving language; these examples deliberately target C++17.

Reaching the recap and completing the quizzes are separate milestones.

    Next lesson: Repeat a Known Range →