include.go

package main

import (
	"os"
	"strconv"
	"strings"
)

type ByNumericalFilename []os.FileInfo

func (nf ByNumericalFilename) Len() int      { return len(nf) }
func (nf ByNumericalFilename) Swap(i, j int) { nf[i], nf[j] = nf[j], nf[i] }
func (nf ByNumericalFilename) Less(i, j int) bool {

	// Use path names
	pathA := nf[i].Name()
	pathB := nf[j].Name()

	// Grab integer value of each filename by parsing the string and slicing off
	// the extension
	a, err1 := strconv.ParseInt(pathA[0:strings.LastIndex(pathA, ".")], 10, 64)
	b, err2 := strconv.ParseInt(pathB[0:strings.LastIndex(pathB, ".")], 10, 64)

	// If any were not numbers sort lexographically
	if err1 != nil || err2 != nil {
		return pathA < pathB
	}

	// Which integer is smaller?
	return a < b
}