gistfile1.txt

// A file
package main

import (
	"fmt"
	"os"
	"regexp"
	"strconv"
	"strings"
)

func check(e error) {
    if e != nil {
        panic(e)
    }
}

func firstRE(r *regexp.Regexp ,s string) string {
	return r.FindString(s)
}

func Reverse(s string) (result string) {
  for _,v := range s {
    result = string(v) + result
  }
  return 
}

func lastRE(r *regexp.Regexp, s string) string {
	return r.FindString(Reverse(s))
}

func calibration(lines []string) (total int) {
	r, _ := regexp.Compile("[0-9]")
	total = 0
	for _, l := range lines {
		firstdigit := firstRE(r,l)
		lastdigit := lastRE(r,l)
		numberString := firstdigit + lastdigit
		number, _ := strconv.Atoi(numberString)
		total += number
	}
	return
	
}
func main() {
	// example := `1abc2
	// pqr3stu8vwx
	// a1b2c3d4e5f
	// treb7uchet`
	// exampleLines := strings.Split(example, "\n")
	// exampleCalibration := calibration(exampleLines)
	// fmt.Println(exampleCalibration)

	dat, err := os.ReadFile("day1.txt")
	check(err)
	lines := strings.Split(string(dat), "\n")
	fmt.Println(calibration(lines))

}