7 lines
500 B
Lua
7 lines
500 B
Lua
--Lazy enumerator of countable infinite set.
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--Pass a function closure for generating the set element-by-element, in order.
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--This function can return a "simple" value followed by an "exact" value
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--Returns a table including:
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-- an array with all elements generated so far (grows as needed upon access)
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local enum = { __index = function( t, n ) for i = #t + 1, n do t[i] = t.next() end return rawget(t, n) end }
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return function(nextElement) return setmetatable( { ["next"] = nextElement }, enum ) end |