serious bit fiddling, div10 using shift magic

forgot that arm has no division (or respectively only later models have)
many magic formulae out there, none seem to work 1000% on the
interpreter. some big 0 ending numbers are 1 off.

lib/soml/parfait/integer.soml

@@ -8,6 +8,88 @@ class Integer < Value
     end
   end
 
+  int high_times( int by_high , int by_low)
+
+    int num_high = self >> 16
+    int num_low  = self & 65535
+
+    int res_high = by_high * num_high
+
+    num_low  = by_high *  num_low
+    num_high = num_high * by_low
+
+    num_high = num_low + num_high
+
+    num_high = num_high >> 16
+
+    res_high = res_high + num_high
+
+    return res_high
+
+  end
+
+  int low_times( int by_high , int by_low)
+
+    int num_high = self >> 16
+    int num_low  = self & 65535
+
+    int res_low = by_low * num_low
+
+    num_low  = by_high *  num_low
+    num_high = num_high * by_low
+
+    num_low = num_low + num_high
+
+    num_low = num_low << 16
+
+    res_low = res_low + num_low
+
+    return res_low
+
+  end
+
+  int div10()
+    int minus_10 = self - 10
+    int me = self
+
+    int tmp = me >> 2
+    me = me - tmp
+
+    tmp = me >> 4
+    me = me + tmp
+
+    tmp = me >> 8
+    me = me + tmp
+
+    tmp = me >> 16
+    me = me + tmp
+    me = me >> 3
+
+    int tmp2 = me << 2
+    tmp2 = me + tmp2
+
+    tmp2 = tmp2 << 1
+    minus_10 =  tmp2 - minus_10
+
+    if_minus(minus_10)
+      me = me + 1
+    end
+    return me
+  end
+
+  int div10_almost()
+    int me = self
+    if_zero( me >> 26 )
+      me = me + 1
+    end
+    int res_high = me.high_times( 26214 , 26215  )
+    int res_low  = self >> 31
+    res_high = res_high >> 2
+
+    return res_high + res_low
+
+  end
+
   Word as_string(Word str)
     if_minus( self - 10 )
       int num = as_char()

lib/soml/parfait/word.soml

@@ -5,7 +5,7 @@ class Word < Object
     word_index = word_index >> 2
     word_index = word_index + 3
     int rest = index - 1
-    rest = rest.mod(4)
+    rest = rest.mod4()
     int char = get_internal(word_index)
     int shifted = 8 * rest
     shifted = char >> shifted
@@ -27,7 +27,7 @@ class Word < Object
     word_index = word_index + 3
 
     int rest = index - 1
-    rest = rest.mod(4)
+    rest = rest.mod4()
 
     int shifted =  rest * 8
     shifted =  char << shifted