128 lines
2.7 KiB
Go
128 lines
2.7 KiB
Go
// Copyright © 2018 Inanc Gumus
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// Learn Go Programming Course
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// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
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//
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// For more tutorials : https://learngoprogramming.com
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// In-person training : https://www.linkedin.com/in/inancgumus/
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// Follow me on twitter: https://twitter.com/inancgumus
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package main
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import (
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"fmt"
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"time"
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"github.com/inancgumus/screen"
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"github.com/mattn/go-runewidth"
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)
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// ---------------------------------------------------------
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// EXERCISE: Single Dimensional
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//
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// In this exercise you will understand why I use
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// a multi-dimensional board slice instead of a
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// single-dimensional one.
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//
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// 1. Remove this:
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// board := make([][]bool, width)
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//
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// 2. Use this:
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// board := make([]bool, width*height)
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//
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// 3. Adjust the rest of the operations in the code to work
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// with this single-dimensional slice.
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//
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// You'll see how hard it becomes to work with it.
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//
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// ---------------------------------------------------------
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func main() {
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const (
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cellEmpty = ' '
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cellBall = '⚾'
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maxFrames = 1200
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speed = time.Second / 20
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// initial velocities
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ivx, ivy = 5, 2
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)
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var (
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px, py int // ball position
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ppx, ppy int // previous ball position
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vx, vy = ivx, ivy // velocities
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cell rune // current cell (for caching)
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)
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// you can get the width and height using the screen package easily:
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width, height := screen.Size()
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// get the rune width of the ball emoji
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ballWidth := runewidth.RuneWidth(cellBall)
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// adjust the width and height
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width /= ballWidth
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height-- // there is a 1 pixel border in my terminal
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// create the board
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board := make([][]bool, width)
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for column := range board {
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board[column] = make([]bool, height)
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}
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// drawing buffer length
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// *2 for extra spaces
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// +1 for newlines
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bufLen := (width*2 + 1) * height
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// create a drawing buffer
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buf := make([]rune, 0, bufLen)
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// clear the screen once
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screen.Clear()
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for i := 0; i < maxFrames; i++ {
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// calculate the next ball position
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px += vx
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py += vy
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// when the ball hits a border reverse its direction
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if px <= 0 || px >= width-ivx {
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vx *= -1
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}
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if py <= 0 || py >= height-ivy {
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vy *= -1
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}
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// remove the previous ball and put the new ball
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board[px][py], board[ppx][ppy] = true, false
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// save the previous positions
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ppx, ppy = px, py
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// rewind the buffer (allow appending from the beginning)
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buf = buf[:0]
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// draw the board into the buffer
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for y := range board[0] {
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for x := range board {
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cell = cellEmpty
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if board[x][y] {
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cell = cellBall
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}
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buf = append(buf, cell, ' ')
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}
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buf = append(buf, '\n')
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}
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// print the buffer
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screen.MoveTopLeft()
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fmt.Print(string(buf))
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// slow down the animation
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time.Sleep(speed)
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}
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}
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