what's wrong with the golang regexp.matchString?

Question

can any one explain why does this match play ?

Source:

package main

import "fmt"
import "regexp"

func main() {
    match, _ := regexp.MatchString("[a-z]+", "test?")
    fmt.Printf("the result of match: %v", match)
}

isn't the golang's regexp.MatchString is fully match? I can't understand and I am a newbie for golang

Answer 1

The regular expression "[az]+" will match "test" is the search text "test?".
Similarly, it will match " testing testing", "2001 a space oddessy", etc.

Go lang's regexp package matches search text according to the syntax and meaning of the regular expression. There isn't a method which itself tries to match the regular expression with the entire search text, and gives up if it can't, unless the regular expression defines that an entire search-text-match is the required behaviour.

The syntax of regular expressions does enable matching the entire search text.

'^' , the start-anchor symbol at the start of the regular expression forces the match to include the start of the search text.
'$' , the end-anchor symbol at the end of the regular expression forces the match to include the end of the search text.
They have different meaning in other positions within a regular expression.

As @TomCooper commented, use both start and end anchors around the regular expression pattern you are looking for. These anchor the enclosed regular expression to the start and end of the search text to ensure the entire search text matches the regular expression.