Reading specific characters from file in Golang - file

Question

I want to read a text file character by character and print invalid input for those characters that exceed "H"and numbers that exceed "8".
eg: my input is
I9,A2
A10,C3
D2,L3
output:
invalid input for all three
package main
import (
"bufio"
"fmt"
"log"
"os"
)
func readLines(path string) ([]string, error) {
file, err := os.Open(path)
if err != nil {
return nil, err
}
defer file.Close()
var lines []string
scanner := bufio.NewScanner(file)
for scanner.Scan() {
lines = append(lines, scanner.Text())
}
return lines, scanner.Err()
}
func main() {
lines, err := readLines("chessin.txt")
if err != nil {
log.Fatalf("readLines: %s", err)
}
var numLines int = len(lines)
for i := 0; i < numLines; i++ {
for j := 0; j < len(lines[i]); j++ {
if j > 'H' {
fmt.Printf("invalid input")
}
}
}
}

Answer 1

You need to edit the inner loop to check for every input line,
and find the number then comma and so, like this working sample code:
package main
import (
"bufio"
"fmt"
"log"
"os"
"strconv"
"strings"
)
func readLines(path string) ([]string, error) {
file, err := os.Open(path)
if err != nil {
return nil, err
}
defer file.Close()
var lines []string
scanner := bufio.NewScanner(file)
for scanner.Scan() {
lines = append(lines, scanner.Text())
}
return lines, scanner.Err()
}
func checkOne(letter byte, number, i, j int) {
if letter > 'H' {
fmt.Printf("invalid input %q # (%d, %d) \n", letter, i, j)
}
if number > 8 {
fmt.Printf("invalid input number %d # (%d, %d) \n", number, i, j+1)
}
}
func main() {
lines, err := readLines("chessin.txt")
if err != nil {
log.Fatalf("readLines: %s", err)
}
var numLines int = len(lines)
for i := 0; i < numLines; i++ {
line := lines[i]
j := 0
comma := strings.IndexByte(line, ',')
if comma == -1 {
log.Fatalf("comma not found at line: %d", i)
}
number, err := strconv.Atoi(line[j+1 : comma])
if err != nil {
log.Fatalf("line:%d err: %s", i, err)
}
checkOne(line[j], number, i, j)
j = comma + 1
number, err = strconv.Atoi(line[j+1:])
if err != nil {
log.Fatalf("line:%d err: %s", i, err)
}
checkOne(line[j], number, i, j)
}
}
input file "chessin.txt":
I9,A2
A10,C3
D2,L3
output:
invalid input 'I' # (0, 0)
invalid input number 9 # (0, 1)
invalid input number 10 # (1, 1)
invalid input 'L' # (2, 3)

Answer 2

You can simplify by using string split and slice. Do not read and store all the values in an array and then loop through them again. Assuming the first character is always Caps and there will be no negative values. Working sample code is as follows:
package main
import (
"bufio"
"fmt"
"os"
"strconv"
"strings"
)
func main() {
file, err := os.Open("chessin.txt")
if err != nil {
fmt.Println(err)
}
defer file.Close()
scanner := bufio.NewScanner(file)
valid := []bool{}
for scanner.Scan() {
strs := strings.Split(scanner.Text(), ",")
valid = append(valid, validateStrings(strs))
}
fmt.Println(valid)
}
func validateStrings(strs []string) bool {
for _, str := range strs {
char := str[0]
num, err := strconv.Atoi(string(str[1:len(str)]))
if err != nil {
fmt.Println("Invalid input")
os.Exit(1)
}
if char < 'A' || char > 'H' || num > 8 || num < 0 {
return false
}
}
return true
}