nitcc: simplify the code of trans generation into two steps

Signed-off-by: Jean Privat <jean@pryen.org>

diff --git a/contrib/nitcc/src/autom.nit b/contrib/nitcc/src/autom.nit
index c419caa..5b545b8 100644 (file)
--- a/contrib/nitcc/src/autom.nit
+++ b/contrib/nitcc/src/autom.nit
@@ -726,22 +726,43 @@ private class DFAGenerator
                                add("\tredef fun trans(char) do\n")
 
                                add("\t\tvar c = char.code_point\n")
-                               var haslast = false
+
+                               # Collect the sequence of tests in the dispatch sequence
+                               # The point here is that for each transition, there is a first and a last
+                               # So holes hare to be identified
+                               var dispatch = new HashMap[Int, nullable State]
+                               var haslast: nullable State = null
+
                                var last = -1
                                for sym, next in trans do
-                                       assert not haslast
+                                       assert haslast == null
                                        assert sym.first > last
-                                       if sym.first > last + 1 then add("\t\tif c <= {sym.first-1} then return null\n")
+                                       if sym.first > last + 1 then
+                                               dispatch[sym.first-1] = null
+                                       end
                                        var l = sym.last
                                        if l == null then
-                                               add("\t\treturn dfastate_{names[next]}\n")
-                                               haslast= true
+                                               haslast = next
                                        else
-                                               add("\t\tif c <= {l} then return dfastate_{names[next]}\n")
+                                               dispatch[l] = next
                                                last = l
                                        end
                                end
-                               if not haslast then add("\t\treturn null\n")
+
+                               # Generate a sequence of `if` for the dispatch
+                               for c, next in dispatch do
+                                       if next == null then
+                                               add("\t\tif c <= {c} then return null\n")
+                                       else
+                                               add("\t\tif c <= {c} then return dfastate_{names[next]}\n")
+                                       end
+                               end
+                               if haslast == null then
+                                       add("\t\treturn null\n")
+                               else
+                                       add("\t\treturn dfastate_{names[haslast]}\n")
+                               end
+
                                add("\tend\n")
                        end
                        add("end\n")