How do I use these in code?

You can use regular expressions in various programming languages. Below are examples in Python, Java, and JavaScript to demonstrate how to use *, ?, and [abc] in code.

Python Example

import re

# Using *
pattern1 = r'a*'
text1 = 'aaab'
matches1 = re.findall(pattern1, text1)
print(matches1)  # Output: ['aaa', '']

# Using ?
pattern2 = r'a?b'
text2 = 'ab'
matches2 = re.findall(pattern2, text2)
print(matches2)  # Output: ['ab']

# Using [abc]
pattern3 = r'[abc]'
text3 = 'xyzabc'
matches3 = re.findall(pattern3, text3)
print(matches3)  # Output: ['a']

Java Example

import java.util.regex.*;

public class RegexExample {
    public static void main(String[] args) {
        // Using *
        String text1 = "aaab";
        Pattern pattern1 = Pattern.compile("a*");
        Matcher matcher1 = pattern1.matcher(text1);
        while (matcher1.find()) {
            System.out.println(matcher1.group());  // Output: aaa, ""
        }

        // Using ?
        String text2 = "ab";
        Pattern pattern2 = Pattern.compile("a?b");
        Matcher matcher2 = pattern2.matcher(text2);
        while (matcher2.find()) {
            System.out.println(matcher2.group());  // Output: ab
        }

        // Using [abc]
        String text3 = "xyzabc";
        Pattern pattern3 = Pattern.compile("[abc]");
        Matcher matcher3 = pattern3.matcher(text3);
        while (matcher3.find()) {
            System.out.println(matcher3.group());  // Output: a
        }
    }
}

JavaScript Example

// Using *
let text1 = 'aaab';
let pattern1 = /a*/g;
let matches1 = text1.match(pattern1);
console.log(matches1);  // Output: ['aaa', '']

// Using ?
let text2 = 'ab';
let pattern2 = /a?b/g;
let matches2 = text2.match(pattern2);
console.log(matches2);  // Output: ['ab']

// Using [abc]
let text3 = 'xyzabc';
let pattern3 = /[abc]/g;
let matches3 = text3.match(pattern3);
console.log(matches3);  // Output: ['a']

Summary

• Use re module in Python, Pattern and Matcher classes in Java, and regex literals in JavaScript to work with regular expressions.
• Adjust the patterns as needed based on your specific requirements.

If you have a specific language or context in mind, let me know for more tailored examples!