Performs a topological sort on input data.
local dump = require "pl.pretty".dump
local tsort = require "resty.tsort"
local graph = tsort.new()
graph:add('a', 'b')
graph:add('b', 'c')
graph:add('0', 'a')
dump(graph:sort())
-- Output:
-- {
-- "0",
-- "a",
-- "b",
-- "c"
-- }
graph:add('1', '2', '3', 'a');
dump(graph:sort())
-- Output:
-- {
-- "0",
-- "1",
-- "2",
-- "3",
-- "a",
-- "b",
-- "c"
-- }
graph:add{'1', '1.5'};
graph:add{'1.5', 'a'};
dump(graph:sort())
-- Output:
-- {
-- "0",
-- "1",
-- "2",
-- "3",
-- "1.5",
-- "a",
-- "b",
-- "c"
-- }
graph:add('first', 'second');
graph:add('second', 'third', 'first');
local sorted, err = graph:sort()
-- Returns:
-- sorted = nil
-- err = "There is a circular dependency in the graph. It is not possible to derive a topological sort."Before developing this library, I asked on #lua channel on Freenode if anyone knows a library that does
topological sort. I also tried to search for a library. Unfortunately I didn't find anything. But, there
was already a library from the great @starius called toposort.
toposort looks really nice and it has a lot more features compared to lua-resty-tsort (also code, 245 lines vs. 58 lines).
So you may want to take a look to that as well especially if you are looking for a more full featured library.
I have not benchmarked these libs or compared them to C-implementation of tsort or other alternatives. If your graph
is not too big, say you use these to sort Javascript / CSS files or something similar, I think the performance
is not an issue.
lua-resty-tsort uses two clause BSD license.
Copyright (c) 2016, Aapo Talvensaari
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