Re: Most efficient way to recognize a line by its first (up to) three characters
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- Subject: Re: Most efficient way to recognize a line by its first (up to) three characters
- From: Tom N Harris <telliamed@...>
- Date: 2014年3月11日 16:52:04 -0400
On Tuesday, March 11, 2014 08:12:49 PM meino.cramer@gmx.de wrote:
> ...and the problem with examples is, that they are examples only :)
> And I have to sent all variations to completly define what I need
> (which I am not allowed to do, by the way).
> Only to describe another variation:
>
> *A N
>
codetree = {
['A'] = { function(str) --[[ handle A ]] end,
['AB'] = { function(str) --[[ handle AB ]] end,
['ABC'] = function(str) --[[ handle ABC ]] end
}
},
['*'] = { --[[ no handler for * ]]
['*A'] = function(str) print[[ handle *A ]] end
}
}
function handlecode(str)
local tree = codetree
for p = 1,#str do
local code = str:sub(1,p)
local nextstate = tree[code] or tree[1]
if type(nextstate) == "function" then -- leaf node
return nextstate(str)
elseif type(nextstate) == "table" then -- branch node
tree = nextstate
else
print("Unknown code")
return
end
end
if tree[1] then
return tree[1](str)
else
print("Unknown code")
end
end
You say you're concerned about the memory of a lookup table so if necessary
you can prune leaves so the leaf functions have to handle multiple codes. And
of course the tree can be constructed from a simple table of code=function
pairs.
--
tom <telliamed@whoopdedo.org>