Shoelace formula for polygonal area: Difference between revisions
Content added Content deleted
m (→{{header|Lua}}: + Lua version) |
m (→{{header|Lua}}: + for loop version) |
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=={{header|Lua}}== |
=={{header|Lua}}== |
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<lang lua>function shoeArea(ps) |
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local function det2(i,j) |
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return ps[i][1]*ps[j][2]-ps[j][1]*ps[i][2] |
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end |
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local sum = #ps>1 and det2(#ps,1) or 0 |
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for i=1,#ps-1 do sum = sum + det2(i,i+1)end |
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return math.abs(0.5 * sum) |
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end</lang> |
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Using an accumulator helper inner function |
Using an accumulator helper inner function |
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<lang lua>function shoeArea(ps) |
<lang lua>function shoeArea(ps) |
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local p = {{3,4}, {5,11}, {12,8}, {9,5}, {5,6}} |
local p = {{3,4}, {5,11}, {12,8}, {9,5}, {5,6}} |
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print(shoeArea(p))-- 30 </lang> |
print(shoeArea(p))-- 30 </lang> |
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both version handle special cases of zero or 1 point. |
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=={{header|Perl 6}}== |
=={{header|Perl 6}}== |
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