- LVAL
 - 
|- (!f b. LVAL f b [] = 0) /\
   !l f b x. LVAL f b (x::l) = f x * b ** LENGTH l + LVAL f b l
 - LVAL_MAX
 - 
|- !l f b. (!x. f x < b) ==> LVAL f b l < b ** LENGTH l
 - LVAL_SNOC
 - 
|- !l h f b. LVAL f b (SNOC h l) = LVAL f b l * b + f h
 - NVAL0
 - 
|- !f b. NVAL f b (WORD []) = 0
 - NVAL1
 - 
|- !f b x. NVAL f b (WORD [x]) = f x
 - NVAL_MAX
 - 
|- !f b. (!x. f x < b) ==> !n (w::PWORDLEN n). NVAL f b w < b ** n
 - NVAL_WCAT
 - 
|- !n m (w1::PWORDLEN n) (w2::PWORDLEN m) f b.
     NVAL f b (WCAT (w1,w2)) = NVAL f b w1 * b ** m + NVAL f b w2
 - NVAL_WCAT1
 - 
|- !w f b x. NVAL f b (WCAT (w,WORD [x])) = NVAL f b w * b + f x
 - NVAL_WCAT2
 - 
|- !n (w::PWORDLEN n) f b x.
     NVAL f b (WCAT (WORD [x],w)) = f x * b ** n + NVAL f b w
 - NVAL_WORDLEN_0
 - 
|- !(w::PWORDLEN 0) fv r. NVAL fv r w = 0
 - NWORD_LENGTH
 - 
|- !n f b m. WORDLEN (NWORD n f b m) = n
 - NWORD_PWORDLEN
 - 
|- !n f b m. PWORDLEN n (NWORD n f b m)