Punchcard

input.go

package main

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

type ScanError string

func (er *ScanError) Error() string {
	return string(*er)
}

type Input struct {
	alphabet string
	lines    []string
}

func getInput() (*Input, error) {
	scanner := bufio.NewScanner(os.Stdin)

	fmt.Print("Alphabet: ")
	scanner.Scan()

	alphaComponents := strings.Split(scanner.Text(), " ")
	if len(alphaComponents) != 2 {
		error := ScanError("Alphabet must have exactly two components.")
		return nil, &error
	}
	alpha := alphaComponents[1]

	fmt.Print("Line count: ")
	scanner.Scan()
	count, err := strconv.Atoi(scanner.Text())
	if err != nil {
		return nil, err
	}

	lines := make([]string, count)
	for i := 0; i < count; i++ {
		fmt.Printf("Line %v: ", i+1)
		scanner.Scan()
		scan := scanner.Text()
		lines[i] = scan
	}

	return &Input{alpha, lines}, nil
}