Conditional Statements

• C++ has the following conditional statements:
  • if, else, else if, switch
• We use Relational operators for conditions :
  • <, <=, >, >=, ==, !=
• We can have multiple conditions using Logical operators :
  • &&, || AND, OR

if Statement

• The if statement is used to execute a block of code only if the specified condition is true.

  if (condition ) {
      // Code to be executed if the condition is true
  }
  

if-else Statement

• The if-else statement allows you to specify two blocks of code.
• One to be executed if the condition is true and another to be executed if the condition is false.

  if (condition) {
      // Code to be executed if the condition is true
  } else {
      // Code to be executed if the condition is false
  }
  

if-else if-else Statement

• The `if-else if-else`` statement allows you to check multiple conditions.
• And execute the corresponding block of code for the first true condition.

  if (condition1 && condition2) {
      // Code to be executed if both condition1 and condition2 are true
  } else if (condition1 || condition2) {
      // Code to be executed if either condition1 or condition1 is true
  } else {
      // Code to be executed if none of the conditions is true
  }
  

Simple Example of Conditional Statement

// conditional_statements.cpp

int num;
cout << "Enter a Number : ";
cin >> num;

if (num > 0) {
    cout << "Number is positive." << endl;
} else if (num < 0) {
    cout << "Number is negative." << endl;
} else {
    cout << "Number is zero." << endl;
}

Short Hand If...Else (Ternary Operator)

• Used to replace multiple lines of code with a single line.
• It is often used to replace simple if else statements
• Syntax : variable = (condition) ? expressionTrue : expressionFalse;

  int marks = 45;
  string result = (marks >= 33) ? "passed" : "failed";
  

Dynamic Declaration

• If a variable is declared in a block, it's memory will be deleted after the program come out from the block.
• It's memory limited to that block only.

  if (condition) {
      int m;
  }
  
  if (int c = a + b; c > 10) {
      // execution
  }
  

Switch Statements

• Switch statement is another way to handle multiple cases or conditions.
• Useful when we have a variable that can take on different values, and we want to perform different actions based on the value of that variable.

  switch (expression) {
      case value1:
          // Code to be executed if expression is equal to value1
          break;
      case value2:
          // Code to be executed if expression is equal to value2
          break;
      // ... more cases ...
      default:
          // Code to be executed if none of the cases match
  }
  

• The break statement is used to exit the switch statement after a case is matched.
• If no match is found, the code under the default label (if present) is executed.
• Only integral type data is allowed in case statement. char and int are integral type data.

• Fall-thru means executing next case also. (Happens when there is no break after case).

  // switch_statement.cpp
  
  char grade;
  
  cout << "Enter your grade (A, B, C, D, or F): ";
  cin >> grade;
  
  switch (grade) {
      case 'A':
          cout << "Excellent!\n";
          break;
      case 'B':
          cout << "Good job!\n";
          break;
      case 'C':
          cout << "Satisfactory.\n";
          break;
      case 'D':
          cout << "Needs improvement.\n";
          break;
      case 'F':
          cout << "Fail.\n";
          break;
      default:
          cout << "Invalid grade entered.\n";
  }
  

Short-Circuiting

• Behavior of logical operators (like && and ||) where the evaluation of the second operand is skipped if the result can be determined by the value of the first operand alone.

• This can be especially useful in conditional statements.

  Logical AND (&&) :

  • If the left operand of && is false, the right operand is not evaluated because the overall result will be false regardless of the value of the right operand.

    if (num > 0 && num < 10) {
        // In the first if statement, if num is not greater than 0, the right operand (num < 10) will not be evaluated due to short-circuiting.
    }
    

  Logical OR (||) :

  • If the left operand of || is true, the right operand is not evaluated because the overall result will be true regardless of the value of the right operand.

    if (num > 0 || num < 10) {
        // In the second if statement, if num is greater than 0, the right operand (num > 10) will not be evaluated due to short-circuiting.
    }