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Control Flow in C++: Conditionals (If/Else, Switch) and Goto
Conditionals are essential for controlling program flow by making decisions based on specific conditions. C++ provides several control flow mechanisms, including if/else, switch, and (though not recommended) goto.
1. Conditional Statements
Conditional statements rely on comparison operators: @article@Comparison Operators
In C++, you can combine multiple conditions using logical operators like && (AND), || (OR). You can also use the keywords and and or. However, && and || are the standard operators.
1.1 If, Else If, Else
Syntax
if (condition1) {
// Executes if condition1 is true
} else if (condition2) {
// Executes if condition1 is false and condition2 is true
} else {
// Executes if both condition1 and condition2 are false
}
Example:
int a = 5, b = 10, c = 3;
if (a < b && b > c) {
std::cout << "Both conditions are true!" << std::endl;
} else if (b == c) {
std::cout << "b is equal to c" << std::endl;
} else {
std::cout << "None of the conditions are true!" << std::endl;
}
1.2 Ternary Operator
The ternary operator is a shorthand way of writing an if-else statement. It can replace multiple lines of code with a single line and is commonly used to simplify if-else statements.
Syntax
variable = (condition) ? expressionTrue : expressionFalse;
Example:
string result = (grade >= 50) ? "passed" : "failed";
2.1 Switch Case
The switch statement provides a way to select one of many code blocks to be executed based on the value of a variable. It's often more efficient than using a series of if-else statements when you have many possible values to check.
Syntax
switch (expression) {
case value1:
// block of code if expression == value1
break;
case value2:
// block of code if expression == value2
break;
// more cases can be added
default:
// block of code if expression doesn't match any case
}
Important!
The break statement is essential because it stops the program from executing the code in the following cases after a match is found. Without it, the program will "fall through" and execute the code in the next case(s), even if they don't match the expression.
Example:
int day = 6;
switch (day) {
case 6:
std::cout << "Saturday" << std::endl;
break; // without this 'break' the program would output "Saturday" and "Sunday"
case 7:
std::cout << "Sunday" << std::endl;
break;
default:
std::cout << "Weekday" << std::endl;
}
2. Goto
The goto statement provides an unconditional jump to another part of the program.
Syntax
The goto statement is used with a label, and it jumps to that label in the code.
goto label;
...
label:
// code to execute after jump
Dangers of Goto
While goto can be useful in very specific situations, its overuse can make your code harder to follow, debug, and maintain. It can lead to "spaghetti code," where the control flow jumps around unpredictably. It's generally recommended to use structured control flow statements like if, switch, and loops instead of goto.
Learn more from the following resources: