Summary  
This chapter covers the if statement as a control-flow construct that evaluates a boolean condition to decide whether to execute a block of code, and notes that braces can be omitted when there is only one statement.  

General domain of usage  
User input validation

The `if` statement is a foundational building block of control flow in most programming languages. It allows a program to make decisions and execute different blocks of code based on whether a given condition is `true` or `false`. The idea behind `if` statements is simple: **If a condition is met, do something, otherwise, don’t.**

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A condition is a boolean expression that evaluates to either `true` or `false`. If it is `true`, the code within the curly braces `{ }` is executed; otherwise, if the condition is `false`, the code inside the block is skipped, and the program continues with the next statement following the `if` block.

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If you have an `if` statement with only **one statement to be executed** when the condition is `true`, you can **omit** the curly braces `{ }`.

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#define CATCH_CONFIG_MAIN
#include <catch2/catch.hpp>

double calculateDiscount(double totalPurchase);

TEST_CASE("Discount for $50 purchase should be $0.0", "[calculateDiscount]") {
    double result = calculateDiscount(50.0);
    REQUIRE(result == Approx(0.0)); // totalPurchase < 100, expected discount: 0
}

TEST_CASE("Discount for $99.99 purchase should be $0.0", "[calculateDiscount]") {
    double result = calculateDiscount(99.99);
    REQUIRE(result == Approx(0.0)); // totalPurchase < 100, expected discount: 0
}

TEST_CASE("Discount for $100 purchase should be $30.0", "[calculateDiscount]") {
    double result = calculateDiscount(100.0);
    REQUIRE(result == Approx(30.0)); // totalPurchase = 100, expected discount: 30% of 100 = 30
}

TEST_CASE("Discount for $150 purchase should be $45.0", "[calculateDiscount]") {
    double result = calculateDiscount(150.0);
    REQUIRE(result == Approx(45.0)); // totalPurchase = 150, expected discount: 30% of 150 = 45
}

TEST_CASE("Discount for $200.75 purchase should be $60.225", "[calculateDiscount]") {
    double result = calculateDiscount(200.75);
    REQUIRE(result == Approx(60.225)); // totalPurchase = 200.75, expected discount: 30% of 200.75 = 60.225
}

test.cpp

Welcome to a beginner-friendly course that will help you learn the core concepts of conditional statements . Whether you're new to programming or looking to improve your understanding of conditional statements and how they influence the flow of your programs, this course is designed to meet your needs.

This is your gateway to understanding the fundamental building blocks of decision making. Gain the essential knowledge to make your programs more intelligent and responsive.

Challenge: If Statement

解答