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--[[
Fuzzel v1.0 - Alexander "Apickx" Pickering
Entered into the public domain June 2, 2016
You are not required to, but consider linking back to the source!
Some helper functions for calculateing distance between two strings
Provides:
fuzzel.LevenshtienDistance_extended(string_first, string_second, number_addcost, number_substituecost, number_deletecost)
Calculates the Levenshtien Distance between two strings, useing the costs given. "Real" Levenshtien Distance uses values 1,1,1 for costs.
returns number_distance
fuzzel.LevenshtienDistance(string_first, strings_second)
Calculates the "real" Levenshtien Distance
returns number_distance
fuzzel.LevensteinRatio(string_first, string_second)
The Levenshtien Ratio divided by the first string's length. Useing a ratio is a decent way to determin if a spelling is "close enough"
returns number_distance
fuzzel.DamerauLevenshtienDistance_extended(string_first, string_second, number_addcost, number_substituecost, number_deletecost, number_transpositioncost)
Damerau-Levenshtien Distance is almost exactly like Levenshtien Distance, with the caveat that two letters next to each other, with swapped positions only counts as "one" cost (in "real" Damerau-Levenshtien Distance)
returns number
fuzzel.DamerauLevenshtienDistance(stirng_first, strings_second)
Calculates the "real" Damerau-Levenshtien Distance
returns number
fuzzel.DamerauLevenshtienRatio(string_first, string_second)
The Damerau-Levenshtien Distance divided by the first string's length
returns number_ratio
fuzzel.HammingDistance(string_first, string_second)
Purely the number of substitutions needed to change one string into another. Note that both strings must be the same length.
returns number_distance
fuzzel.HammingRatio(string_first, string_second)
The hamming distance divided by the length of the first string
returns number_ratio
fuzzel.FuzzySearchDistance(string_needle, vararg_in)
in may be either a table, or a list of arguments. fuzzel.FuzzySearchDistance will find the string that most closely resembles needle, based on Damerau-Levenshtien Distance
returns string_closest, number_distance
fuzzel.FuzzySearchRatio(string_needle, vararg_in)
in may be either a table, or a list of arguments. Same as above, except it returns the string with the closest Damerau-Levenshtien ratio.
returns string_closest, nubmer_ratio
]]
local strlen,chrat,min,asrt,prs,iprs,typ,upack = string.len,string.byte,math.min,assert,pairs,ipairs,type,unpack
module("fuzzel")
local function genericDistance( stringa, stringb, addcost, subcost, delcost, ...)
--Length of each string
local salen, sblen = strlen(stringa), strlen(stringb)
--Create a 0 matrix the size of len(a) x len(b)
local dyntbl = {}
for i = 0,salen do
dyntbl[i] = {}
for j = 0,sblen do
dyntbl[i][j] = 0
end
end
--Initalize the matrix
for i = 1,salen do
dyntbl[i][0] = i
end
for j = 1,sblen do
dyntbl[0][j] = j
end
--And build up the matrix based on costs-so-far
for j = 1,sblen do
for i = 1,salen do
local ca = chrat(stringa,i)
local cb = chrat(stringb,j)
dyntbl[i][j] = min(
dyntbl[i-1][j] + delcost, --deletion
dyntbl[i][j-1] + addcost, --insertion
dyntbl[i-1][j-1] + (ca == cb and 0 or subcost) --substituion
)
if arg[1] and i > 1 and j > 1 and ca == chrat(stringb,j-1) and chrat(stringa,i-1) == cb then
dyntbl[i][j] = min(dyntbl[i][j],
dyntbl[i-2][j-2] + (ca == cb and 0 or arg[2])) --transposition
end
end
end
return dyntbl[salen][sblen]
end
function LevenshtienDistance_extended(stringa, stringb, addcost, subcost, delcost)
return genericDistance(stringa, stringb, addcost, subcost, delcost)
end
function LevenshtienDistance(stringa,stringb)
return LevenshtienDistance_extended(stringa,stringb,1,1,1)
end
--The distance as a ratio of stringa's length
function LevenshteinRatio(stringa,stringb)
return LevenshtienDistance(stringa,stringb) / strlen(stringa)
end
--Almost the same as LevenshtienDistance, but considers two characters swaped as only "one" mistake
function DamerauLevenshtienDistance_extended(stringa, stringb, addcost, subcost, delcost, trncost)
return genericDistance(stringa,stringb,addcost,subcost,delcost,true,trncost)
end
function DamerauLevenshtienDistance(stringa,stringb)
return DamerauLevenshtienDistance_extended(stringa,stringb,1,1,1,1)
end
function DamerauLevenshtienRatio(stringa,stringb)
return DamerauLevenshtienDistance(stringa,stringb) / strlen(stringa)
end
--Purely the number of mistakes
function HammingDistance(stringa,stringb)
local len = strlen(stringa)
asrt(len == strlen(stringb),"Hamming Distance cannot be calculated on two strings of different lengths:\"" .. stringa .. "\" \"" .. stringb .. "\"")
local dist = 0
for i = 1,len do
dist = dist + (chrat(stringa,i) ~= chrat(stringb,i) and 1)
end
return dist
end
function HammingRatio(stringa,stringb)
return HammingDistance(stringa,stringb) / strlen(stringa)
end
local function FuzzySearch(str,func,...)
local itrfunc = typ(arg[1]) == "table" and prs or iprs
local tmin = func(arg[1],str)
local sout = arg[1]
for k,v in itrfunc(arg) do
local t = func(v,str)
if t < tmin then
tmin = t
sout = v
end
end
return sout, tmin
end
function FuzzySearchDistance(str,...)
return upack{FuzzySearch(str,DamerauLevenshtienDistance,...)}
end
function FuzzySearchRatio(str,...)
return upack{FuzzySearch(str,DamerauLevenshtienRatio,...)}
end
--Some easy-to-use mnemonics
ld_e = LevenshtienDistance_extended
ld = LevenshtienDistance
lr = LevensteinRatio
dld_e = DamerauLevenshtienDistance_extended
dld = DamerauLevenshtienDistance
dlr = DamerauLevenshtienRatio
hd = HammingDistance
hr = HammingRatio
fsd = FuzzySearchDistance
fsr = FuzzySearchRatio
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