[go-nuts] Regexp question

[Jan Mercl]

This code (A)

        package main

        import (
                "fmt"
                "regexp"
        )

        func main() {
                fmt.Printf("%v",
regexp.MustCompile(`a*`).FindAllStringIndex(`baaab`, -1))
        }

(https://play.golang.org/p/WeyStT0Gbn)

Produces

        [[0 0] [1 4] [5 5]]

Why there is no match at [4 4]? That's at the (start of the) second letter
b in the text, analogically to the first match [0, 0]. Am I missing
something or is it a bug?

In a similar program, the symmetry is present (B)

        package main

        import (
                "fmt"
                "regexp"
        )

        func main() {
                fmt.Println(regexp.MustCompile(`a*`).FindAllStringIndex(``,
-1))

fmt.Println(regexp.MustCompile(`a*`).FindAllStringIndex(`b`, -1))

fmt.Println(regexp.MustCompile(`a*`).FindAllStringIndex(`bb`, -1))

fmt.Println(regexp.MustCompile(`a*`).FindAllStringIndex(`bbb`, -1))
        }

(https://play.golang.org/p/m0kbrNQp21)

Output

        [[0 0]]
        [[0 0] [1 1]]
        [[0 0] [1 1] [2 2]]
        [[0 0] [1 1] [2 2] [3 3]]

Thanks in advance to anyone enlightening me.

FTR: The regular expression and the test text in (A) is part of the regexp
package tests at [0].

  [0]:
https://github.com/golang/go/blob/0d818588685976407c81c60d2fda289361cbc8ec/src/regexp/find_test.go#L44

-- 

-j

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