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local module = {}
setmetatable(module, {__index=_G})
setfenv(1, module)
local Grammar = {}
function module.createGrammar(nonterminals, triggers)
local self = {
nonterminals = nonterminals,
triggers = triggers,
context = {},
}
setmetatable(self, {__index=Grammar})
return self
end
function Grammar.pushContext(self)
local newContext = {}
setmetatable(newContext, {__index=self.context})
self.context = newContext
end
function Grammar.popContext(self)
local mt = getmetatable(self.context)
local oldContext = (mt and mt.__index) or {}
self.context = oldContext
end
function Grammar.expandSymbol(self, sequence, index, expansion)
table.remove(sequence, index)
for i=1,#expansion do
table.insert(sequence, index+i-1, expansion[i])
end
end
function Grammar.expandSequence(self, sequence, n)
local i = 1
while i <= #sequence do
local choices = self.nonterminals[sequence[i]] or self.context[sequence[i]]
if choices then
local trigger = self.triggers[sequence[i]]
if trigger then trigger(self) end
if #choices == 1 then
self:expandSymbol(sequence, i, choices[1])
return true, 0
else
local choice = choices[1 + (n % #choices)]
self:expandSymbol(sequence, i, choice)
return true, 1
end
else
i = i+1
end
end
return false, 0
end
function Grammar.expand(self, genome, maxLength)
maxLoops = maxLoops or 2
local sequence = { '<start>' }
local geneIndex = 0
local count = 0
local continue = true
while continue do
local gene
if (count > maxLoops * #genome) then
gene = 0
else
gene = genome[1 + (geneIndex % #genome)]
end
local increment
continue, increment = self:expandSequence(sequence, gene)
if not continue then break end
geneIndex = geneIndex+increment
count = count + 1
end
local result = ''
for _, s in ipairs(sequence) do
result = result .. s
end
return result
end
return module
|
