regex.go

package main

import (
	"bytes"
	"fmt"
	"regexp"
)

func main() {

	// Tesst whether a pattern matches a string.
	match, _ := regexp.MatchString("p([a-z]+)ch", "peach")
	fmt.Println(match)

	// Above we used a string pattern directly,
	// but for other regexp tasks you’ll need to
	// Compile an optimized Regexp struct.
	r, _ := regexp.Compile("p([a-z]+)ch")

	// Many methods are available on these structs.
	// Here’s a match test like we saw earlier.
	fmt.Println(r.MatchString("peach"))

	// This finds the match for the regexp.
	fmt.Println(r.FindString("peach punch"))

	// This also finds the first match but returns the start
	// and end indexes for the match instead of the matching text.
	fmt.Println(r.FindStringIndex("peach punch"))

	// The Submatch variants include information about both the whole-pattern matches
	// and the submatches within those matches.
	// For example this will return information for both p([a-z]+)ch and ([a-z]+).
	fmt.Println(r.FindStringSubmatch("peach punch"))

	// Similarly this will return information about the indexes of
	// matches and submatches.
	fmt.Println(r.FindStringSubmatchIndex("peach punch"))

	// The All variants of these functions apply to all matches in the input,
	// not just the first. For example to find all matches for a regexp.
	fmt.Println(r.FindAllString("peach punch pinch", -1))

	// These All variants are available for the other functions we saw above as well.
	fmt.Println(r.FindAllStringSubmatchIndex("peach punch pinch", -1))

	// Providing a non-negative integer as the second argument to these functions will limit the number of matches.
	fmt.Println(r.FindAllString("peach punch pinch", 2))

	// Our examples above had string arguments and used names like MatchString.
	// We can also provide []byte arguments and drop String from the function name.
	fmt.Println(r.Match([]byte("peach")))

	// When creating global variables with regular expressions you can use
	// the MustCompile variation of Compile.
	// MustCompile panics instead of returning an error,
	// which makes it safer to use for global variables.
	r = regexp.MustCompile("p([a-z]+)ch")
	fmt.Println(r)

	// The regexp package can also be used to replace subsets of strings with other values.
	fmt.Println(r.ReplaceAllString("a peach", "<fruit>"))

	// The Func variant allows you to transform matched text with a given function.
	in := []byte("a peach")
	out := r.ReplaceAllFunc(in, bytes.ToUpper)
	fmt.Println(string(out))

}