How to extract substrings [duplicate] - regex

Question

This question already has answers here:
How to extract a floating number from a string [duplicate]
(7 answers)
Closed 2 years ago.
I wrote in Go the following code to extract two values ​​inside the string.
I used two regexp to seek the numbers (float64).
The first result is the correct, only de number. But the second is wrong.
This is the code:
package main
import (
"fmt"
"regexp"
)
func main() {
// RegExp utiliza la sintaxis RE2
pat1 := regexp.MustCompile(`[^m2!3d][\d\.-]+`)
s1 := pat1.FindString(`Torre+Eiffel!8m2!3d-48.8583701!4d-2.2944813!3m4!1s0x47e66e2964e34e2d:0x8ddca9ee380ef7e0!8m2!3d-48.8583701!4d-2.2944813`)
pat2 := regexp.MustCompile(`[^!4d][\d\.-]+`)
s2 := pat2.FindString(`Torre+Eiffel!8m2!3d-48.8583701!4d-2.2944813!3m4!1s0x47e66e2964e34e2d:0x8ddca9ee380ef7e0!8m2!3d-48.8583701!4d-2.2944813`)
fmt.Println(s1) // Print -> -48.8583701
fmt.Println(s2) // Print -> m2 (The correct answer is "-2.2944813")
}
Here I modify the syntax
pat2 := regexp.MustCompile(!4d[\d\.-]+)
and I get the following answer:
!4d-2.2944813
but it's not what I'm expecting.

Answer 1

It seems like you are only interessed in the latitude and longitute of an attraction and not really in the regex.
Maybe you just use something like this:
package main
import (
"fmt"
"strconv"
"strings"
)
var replacer = strings.NewReplacer("3d-", "", "4d-", "")
func main() {
var str = `Torre+Eiffel!8m2!3d-48.8583701!4d-2.2944813!3m4!1s0x47e66e2964e34e2d:0x8ddca9ee380ef7e0!8m2!3d-48.8583701!4d-2.2944813`
fmt.Println(getLatLong(str))
}
func getLatLong(str string) (float64, float64, error) {
parts := strings.Split(str, "!")
if latFloat, err := strconv.ParseFloat(replacer.Replace(parts[2]), 64); err != nil {
return 0, 0, err
} else if lngFloat, err := strconv.ParseFloat(replacer.Replace(parts[3]), 64); err != nil {
return 0, 0, err
} else {
return latFloat, lngFloat, nil
}
}
https://play.golang.org/p/UOIwGbl6nrb

Answer 2

You where almost there. Try (?m)(?:3d|4d)-([\d\.-]+)(?:!|$)
https://regex101.com/r/8KgirB/1
All you need is a matching group around the [\d\.-]+ part. With this group you are able to access it directly
package main
import (
"fmt"
"regexp"
)
func main() {
var re = regexp.MustCompile(`(?m)(?:3d|4d)-([\d\.-]+)!`)
var str = `Torre+Eiffel!8m2!3d-48.8583701!4d-2.2944813!3m4!1s0x47e66e2964e34e2d:0x8ddca9ee380ef7e0!8m2!3d-48.8583701!4d-2.2944813`
for _, match := range re.FindAllStringSubmatch(str, -1) {
fmt.Println(match[1])
}
}