bigdigits.go

package main

import (
    "fmt"
    "log"
    "os"
    "path/filepath"
)

var bigDigits = [][]string{
    {"  000  ",
        " 0   0 ",
        "0     0",
        "0     0",
        "0     0",
        " 0   0 ",
        "  000  "},
    {"  111  ",
        "11111  ",
        "  111  ",
        "  111  ",
        "  111  ",
        "  111  ",
        "1111111"},
    {"  2222 ",
        "22   22",
        "    22 ",
        "   22  ",
        "  22   ",
        " 22    ",
        "2222222"},
    {" 33333 ",
        "33   33",
        "    33 ",
        "   33  ",
        "    33 ",
        "33   33",
        " 33333 "},
    {"    44 ",
        "   444 ",
        "  4 44 ",
        " 4  44 ",
        "4444444",
        "    44 ",
        "    44 "},
    {"5555555",
        "55     ",
        "55     ",
        " 55555 ",
        "     55",
        "55   55",
        " 55555 "},
    {"   66  ",
        "  66   ",
        " 66    ",
        "666666 ",
        "66   66",
        " 66  66",
        "  666  "},
    {"7777777",
        "     77",
        "    77 ",
        "    77 ",
        "   77  ",
        "   77  ",
        "   77  "},
    {"  888  ",
        " 8   8 ",
        " 8   8 ",
        "  888  ",
        " 8   8 ",
        " 8   8 ",
        "  888  "},
    {"  9999 ",
        " 9    9",
        " 9    9",
        "  99999",
        "    99 ",
        "   99  ",
        "  99   "},
}

func main() {

    // If only one argument is passed (Args[0] holds program's name)
    if len(os.Args) == 1 {
        fmt.Printf("usage: %s <whole-number>\n", filepath.Base(os.Args[0]))
        os.Exit(1)
    }

    // Set the stringOfDigits to be the second argument of the command-line
    stringOfDigits := os.Args[1]

    // For a variable row = 0, loop over the items in the first slot of bigDigits
    // for row = 0; row < len(bigDigits[0]); row++
    for row := range bigDigits[0] {

        // Set line to be an empty string
        line := ""

        // Iterate over each digit in stringOfDigits
        for column := range stringOfDigits {

            // stringOfDigits[0], for example, returns a single character represented by a byte (since that's what strings are)
            digit := stringOfDigits[column] - '0'

            // If the digit is between 0 and 9...
            // Go converts between uint8 and byte
            if 0 <= digit && digit <= 9 {
                // Why concatenate the space?
                // Because it adds a space at the end of each row (and therefore between each big digit)
                line += bigDigits[digit][row] + " "
            } else {
                log.Fatal("invalid whole number")
            }
        }
        fmt.Println(line)
    }
}