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added functional.map_pairs
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@ -318,6 +318,24 @@ end
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functional.map_chain = functional.chain
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--maps a sequence {a, b, c, d} -> { f(a, b), f(a, c), f(a, d), f(b, c), f(b, d), f(c, d) }
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-- ie all distinct pairs are mapped, useful for any N^2 dataset (eg finding neighbours)
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function functional.map_pairs(t, f)
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local result = {}
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for i = 1, #t do
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for j = i+1, #t do
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local a = t[i]
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local b = t[j]
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local v = f(a, b)
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if v ~= nil then
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table.insert(result, v)
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end
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end
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end
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return result
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end
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-----------------------------------------------------------
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--generating data
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