How is the case statement used in the ENGLISH_CALC function?

In the ENGLISH_CALC function, the case statement is used to handle different arithmetic operations based on the value of the operation parameter. Here's how it works:

Structure of the case Statement

The case statement evaluates the value of operation and executes the corresponding block of code for each case. If none of the cases match, it executes the default block (the * case).

Example Breakdown

Here’s the relevant part of the ENGLISH_CALC function:

case $operation in
    plus)
        result=$((num1 + num2))
        echo "$num1 + $num2 = $result"
        ;;
    minus)
        result=$((num1 - num2))
        echo "$num1 - $num2 = $result"
        ;;
    times)
        result=$((num1 * num2))
        echo "$num1 * $num2 = $result"
        ;;
    *)
        echo "Invalid operation. Please use 'plus', 'minus', or 'times'."
        return 1
        ;;
esac

How It Works:

1. Pattern Matching: The case statement checks the value of operation against the specified patterns (plus, minus, times).
2. Execution:
   • If operation is plus, it calculates the sum of num1 and num2.
   • If operation is minus, it calculates the difference.
   • If operation is times, it calculates the product.
3. Default Case: If operation does not match any of the specified patterns, the * case is executed, which prints an error message and returns a non-zero status to indicate an error.

Summary

The case statement in the ENGLISH_CALC function provides a clean and efficient way to handle multiple operations based on user input, making the function easy to extend and maintain.