remove div and add div10

general division is for another day, the 10 version is manageable
also same code produces mod10
wip

lib/soml/parfait/integer.soml

@@ -13,7 +13,7 @@ class Integer < Value
       int num = as_char()
       str = str.push_char( num )
     else
-      int rest = self / 10
+      int rest = self.div10()
       str = rest.as_string( str )
       rest = rest * 10
       rest = self - rest
@@ -33,14 +33,7 @@ class Integer < Value
     return self
   end
 
-  int div( Integer by)
-    int ret = self / by
-    return ret
-  end
-
-  int mod(Integer by)
-    int base = self / by
-    base = base * by
-    return self - base
+  int mod4()
+    return self & 3
   end
 end

lib/soml/parfait/word.soml

@@ -2,7 +2,7 @@ class Word < Object
 
   int char_at(int index)
     int word_index = index - 1
-    word_index = word_index / 4
+    word_index = word_index >> 2
     word_index = word_index + 3
     int rest = index - 1
     rest = rest.mod(4)
@@ -23,7 +23,7 @@ class Word < Object
     self.set_length(index)
 
     int word_index = index - 1
-    word_index = word_index / 4
+    word_index = word_index >> 2
     word_index = word_index + 3
 
     int rest = index - 1