132 lines
3.0 KiB
Go
132 lines
3.0 KiB
Go
/*
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Copyright © 2025 filifa
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This program is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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package cmd
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import (
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"bufio"
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"fmt"
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"os"
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"strconv"
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"strings"
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"github.com/spf13/cobra"
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)
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var shoelaceFile string
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type point struct {
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x float64
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y float64
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}
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func splitLines(file *os.File) []string {
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slice := make([]string, 0)
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scanner := bufio.NewScanner(file)
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for scanner.Scan() {
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slice = append(slice, scanner.Text())
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}
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return slice
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}
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func readFromFile(filepath string) ([]point, error) {
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points := make([]point, 0)
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file, err := os.Open(filepath)
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if err != nil {
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return points, err
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}
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defer file.Close()
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lines := splitLines(file)
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for _, line := range lines {
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fields := strings.Fields(line)
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x, err := strconv.ParseFloat(fields[0], 64)
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if err != nil {
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return points, err
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}
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y, err := strconv.ParseFloat(fields[1], 64)
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if err != nil {
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return points, err
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}
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points = append(points, point{x, y})
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}
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return points, nil
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}
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func area(points []point) float64 {
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total := float64(0)
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n := len(points)
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for i, p := range points {
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q := points[(i+1)%n]
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total += (p.y + q.y) * (p.x - q.x)
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}
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return total / 2
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}
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func shoelace(cmd *cobra.Command, args []string) {
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var coordinates []point
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var err error
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if shoelaceFile != "" {
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coordinates, err = readFromFile(shoelaceFile)
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if err != nil {
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cobra.CheckErr(err)
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}
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} else {
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cobra.CheckErr("filename required")
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}
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fmt.Println(area(coordinates))
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}
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// shoelaceCmd represents the shoelace command
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var shoelaceCmd = &cobra.Command{
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Use: "shoelace -f FILE",
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Short: "Compute the area of a simple polygon from the vertex coordinates",
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Long: `Compute the area of a simple polygon from the vertex coordinates.
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Put each point on its own line, with each coordinate separated by whitespace. For example, a file with
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1 6
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3 1
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7 2
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4 4
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8 5
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will output an area of 16.5.`,
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Run: shoelace,
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}
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func init() {
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rootCmd.AddCommand(shoelaceCmd)
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// Here you will define your flags and configuration settings.
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// Cobra supports Persistent Flags which will work for this command
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// and all subcommands, e.g.:
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// shoelaceCmd.PersistentFlags().String("foo", "", "A help for foo")
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// Cobra supports local flags which will only run when this command
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// is called directly, e.g.:
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// shoelaceCmd.Flags().BoolP("toggle", "t", false, "Help message for toggle")
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shoelaceCmd.Flags().StringVarP(&shoelaceFile, "file", "f", "", "file with coordinates")
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// TODO: add flag for inputting coordinates from cli
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}
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