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<h1>Lua-System</h1>
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<li><strong>spiral_snake.lua</strong></li>
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<h2>spiral_snake.lua</h2>
<pre>
<span class="keyword">local</span> sys = <span class="global">require</span> <span class="string">"system"</span>
<span class="global">print</span> <span class="string">[[
This example will draw a snake like spiral on the screen. Showing ANSI escape
codes for moving the cursor around.
]]</span>
<span class="comment">-- backup term settings with auto-restore on exit
</span>sys.<span class="function-name">autotermrestore</span>()
<span class="comment">-- setup Windows console to handle ANSI processing
</span>sys.<span class="function-name">setconsoleflags</span>(<span class="global">io</span>.stdout, sys.<span class="function-name">getconsoleflags</span>(<span class="global">io</span>.stdout) + sys.COF_VIRTUAL_TERMINAL_PROCESSING)
<span class="comment">-- start drawing the spiral.
</span><span class="comment">-- start from current pos, then right, then up, then left, then down, and again.
</span><span class="keyword">local</span> x, y = <span class="number">1</span>, <span class="number">1</span> <span class="comment">-- current position
</span><span class="keyword">local</span> dx, dy = <span class="number">1</span>, <span class="number">0</span> <span class="comment">-- direction after each step
</span><span class="keyword">local</span> wx, wy = <span class="number">30</span>, <span class="number">30</span> <span class="comment">-- width and height of the room
</span><span class="keyword">local</span> mx, my = <span class="number">1</span>, <span class="number">1</span> <span class="comment">-- margin
</span>
<span class="comment">-- commands to move the cursor
</span><span class="keyword">local</span> move_left = <span class="string">"\27[1D"</span>
<span class="keyword">local</span> move_right = <span class="string">"\27[1C"</span>
<span class="keyword">local</span> move_up = <span class="string">"\27[1A"</span>
<span class="keyword">local</span> move_down = <span class="string">"\27[1B"</span>
<span class="comment">-- create room: 30 empty lines
</span><span class="global">print</span>((<span class="string">"\n"</span>):<span class="function-name">rep</span>(wy))
<span class="keyword">local</span> move = move_right
<span class="keyword">while</span> wx > <span class="number">0</span> <span class="keyword">and</span> wy > <span class="number">0</span> <span class="keyword">do</span>
sys.<span class="function-name">sleep</span>(<span class="number">0.01</span>) <span class="comment">-- slow down the drawing a little
</span> <span class="global">io</span>.<span class="function-name">write</span>(<span class="string">"*"</span> .. move_left .. move )
<span class="global">io</span>.<span class="function-name">flush</span>()
x = x + dx
y = y + dy
<span class="keyword">if</span> x > wx <span class="keyword">and</span> move == move_right <span class="keyword">then</span>
<span class="comment">-- end of move right
</span> dx = <span class="number">0</span>
dy = <span class="number">1</span>
move = move_up
wy = wy - <span class="number">1</span>
my = my + <span class="number">1</span>
<span class="keyword">elseif</span> y > wy <span class="keyword">and</span> move == move_up <span class="keyword">then</span>
<span class="comment">-- end of move up
</span> dx = -<span class="number">1</span>
dy = <span class="number">0</span>
move = move_left
wx = wx - <span class="number">1</span>
mx = mx + <span class="number">1</span>
<span class="keyword">elseif</span> x < mx <span class="keyword">and</span> move == move_left <span class="keyword">then</span>
<span class="comment">-- end of move left
</span> dx = <span class="number">0</span>
dy = -<span class="number">1</span>
move = move_down
wy = wy - <span class="number">1</span>
my = my + <span class="number">1</span>
<span class="keyword">elseif</span> y < my <span class="keyword">and</span> move == move_down <span class="keyword">then</span>
<span class="comment">-- end of move down
</span> dx = <span class="number">1</span>
dy = <span class="number">0</span>
move = move_right
wx = wx - <span class="number">1</span>
mx = mx + <span class="number">1</span>
<span class="keyword">end</span>
<span class="keyword">end</span>
<span class="global">io</span>.<span class="function-name">write</span>(move_down:<span class="function-name">rep</span>(<span class="number">15</span>))
<span class="global">print</span>(<span class="string">"\nDone!"</span>)</pre>
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