1 files changed, 19 insertions, 5 deletions
diff --git a/grammar.lua b/grammar.lua
index 27e75f7..286723d 100644
--- a/grammar.lua
+++ b/grammar.lua
@@ -5,17 +5,29 @@ setfenv(1, module)
 
 local Grammar = {}
 
-function module.createGrammar(nonterminals, functions, terminals)
+function module.createGrammar(nonterminals, triggers)
   local self = {
     nonterminals = nonterminals,
-    functions = functions,
-    terminals = terminals,
+    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
@@ -27,8 +39,10 @@ end
 function Grammar.expandSequence(self, sequence, n)
   local i = 1
   while i <= #sequence do
-    local choices = self.nonterminals[sequence[i]]
+    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
@@ -66,7 +80,7 @@ function Grammar.expand(self, genome, maxLength)
   end
   local result = ''
   for _, s in ipairs(sequence) do
-    result = result .. s .. ' '
+    result = result .. s
   end
   return result
 end