Concatenation (AND) of regexes in Go (Golang)

Overview

It is similar to AND operator. For example, if there are two regexes r1 and r2, the concatenation of regexes will be represented as below.

r1r2

It will match regex r1 followed by r2. Both r1 and r2 should be valid regexes. Basically, if string s matches regex r1 and string t matches regex r2, then string st will match r1r2.

Program

Here is the example program for the same

package main

import (
	"fmt"
	"regexp"
)

func main() {
	first := "abc"
	second := "xyz"
	sampleRegex := regexp.MustCompile(first + second)

	match := sampleRegex.Match([]byte("abcxyz"))
	fmt.Println(match)

	match = sampleRegex.Match([]byte("abc"))
	fmt.Println(match)

	match = sampleRegex.Match([]byte("xyz"))
	fmt.Println(match)

	match = sampleRegex.Match([]byte("abd"))
	fmt.Println(match)
}

Output

true
false
false
false

It only matches

abcxyz

We first compile the given regex using the MustCompile function. This function panics if the given regex is not valid. After it is able to successfully compile the given regex, it returns the instance of regexp struct.

sampleRegexp := regexp.MustCompile(first + second)

We can call the Match method on the regexp instance to match the given pattern with the regex. It returns true if the regex matches with the input string otherwise false. We need to pass in bytes of the input string to this method.

match := sampleRegexp.Match([]byte("abcxyz"))

Concatenation can also be done between more than three regexes. Below is an example for the same

package main

import (
    "fmt"
    "regexp"
)
func main() {
    first := "abc"
    second := "xyz"
    third := "123"
    sampleRegex := regexp.MustCompile(first + second + third)

    match := sampleRegex.Match([]byte("abcxyz123"))
    fmt.Println(match)

    match = sampleRegex.Match([]byte("abc"))
    fmt.Println(match)

    match = sampleRegex.Match([]byte("xyz"))
    fmt.Println(match)

    match = sampleRegex.Match([]byte("abcxyz"))
    fmt.Println(match)

    match = sampleRegex.Match([]byte("abd"))
    fmt.Println(match)
}

Output

true
false
false
false
false

It only matches

abcxyz123

Also, check out our Golang advance tutorial Series – Golang Advance Tutorial