How to perform text indexing and searching with regular expressions in Go?

To perform text indexing and searching with regular expressions in Go, you can use the built-in regexp package. This package includes functions and types to compile regular expressions and perform searches on text.

Here's an example to illustrate text indexing and searching with regular expressions in Go:

First, import the regexp package:

import (
	"fmt"
	"regexp"
)

Compile the regular expression pattern using regexp.Compile() function:

pattern := regexp.MustCompile(`hello`)

Create a string to search within:

text := "Hello, how are you? Would you like to say hello?"

Perform a search on the text using FindAllStringIndex() function:

matches := pattern.FindAllStringIndex(text, -1)

The FindAllStringIndex() function returns a slice of indices representing the start and end positions of the matched substrings. The -1 argument specifies to find all matches, regardless of the limit.

Iterate over the matches and print the index and the matched substring:

for _, match := range matches {
	start := match[0]
	end := match[1]
	fmt.Printf("Match at index %d: %s\n", start, text[start:end])
}

This will output:

Match at index 0: Hello
Match at index 32: hello

You can use regular expression syntax to match more complex patterns with wildcards, character classes, quantifiers, etc. The regexp package has various functions and types to handle more advanced features.

Note: Regular expressions can be powerful but also complex. It's important to properly understand and test your regular expressions to ensure correct behavior and avoid unexpected results.