src/HOL/Word/WordExamples.thy

* HOL-Word:
New extensive library and type for generic, fixed size machine
words, with arithemtic, bit-wise, shifting and rotating operations,
reflection into int, nat, and bool lists, automation for linear
arithmetic (by automatic reflection into nat or int), including
lemmas on overflow and monotonicity. Instantiated to all appropriate
arithmetic type classes, supporting automatic simplification of
numerals on all operations. Jointly developed by NICTA, Galois, and
PSU.

* still to do: README.html/document + moving some of the generic lemmas
to appropriate place in distribution

(* 
  ID:     $Id$
  Author: Gerwin Klein, NICTA

  Examples demonstrating and testing various word operations.
*)

theory WordExamples imports WordMain
begin

-- "modulus"

lemma "(27 :: 4 word) = -5" by simp

lemma "(27 :: 4 word) = 11" by simp

lemma "27 \<noteq> (11 :: 6 word)" by simp

-- "signed"
lemma "(127 :: 6 word) = -1" by simp

-- "number ring simps"
lemma 
  "27 + 11 = (38::'a::len word)"
  "27 + 11 = (6::5 word)"
  "7 * 3 = (21::'a::len word)"
  "11 - 27 = (-16::'a::len word)"
  "- -11 = (11::'a::len word)"
  "-40 + 1 = (-39::'a::len word)"
  by simp_all

lemma "word_pred 2 = 1" by simp

lemma "word_succ -3 = -2" by simp
  
lemma "23 < (27::8 word)" by simp
lemma "23 \<le> (27::8 word)" by simp
lemma "\<not> 23 < (27::2 word)" by simp
lemma "0 < (4::3 word)" by simp

-- "ring operations"

lemma "a + 2 * b + c - b = (b + c) + (a :: 32 word)" by simp

-- "casting"

lemma "uint (234567 :: 10 word) = 71" by simp
lemma "uint (-234567 :: 10 word) = 953" by simp
lemma "sint (234567 :: 10 word) = 71" by simp
lemma "sint (-234567 :: 10 word) = -71" by simp

lemma "unat (-234567 :: 10 word) = 953" by simp

lemma "ucast (0b1010 :: 4 word) = (0b10 :: 2 word)" by simp
lemma "ucast (0b1010 :: 4 word) = (0b1010 :: 10 word)" by simp
lemma "scast (0b1010 :: 4 word) = (0b111010 :: 6 word)" by simp

-- "reducing goals to nat or int and arith:"
lemma "i < x ==> i < (i + 1 :: 'a :: len word)" by unat_arith
lemma "i < x ==> i < (i + 1 :: 'a :: len word)" by uint_arith

-- "bool lists"

lemma "of_bl [True, False, True, True] = (0b1011::'a::len word)" by simp

lemma "to_bl (0b110::4 word) = [False, True, True, False]" by simp

-- "this is not exactly fast, but bearable"
lemma "of_bl (replicate 32 True) = (0xFFFFFFFF::32 word)" by simp

-- "this works only for replicate n True"
lemma "of_bl (replicate 32 True) = (0xFFFFFFFF::32 word)"
  by (unfold mask_bl [symmetric]) (simp add: mask_def)


-- "bit operations"

lemma "0b110 AND 0b101 = (0b100 :: 32 word)" by simp

lemma "0b110 OR 0b011 = (0b111 :: 8 word)" by simp

lemma "0xF0 XOR 0xFF = (0x0F :: byte)" by simp

lemma "NOT (0xF0 :: 16 word) = 0xFF0F" by simp

lemma "(-1 :: 32 word) = 0xFFFFFFFF" by simp

lemma "(0b0010 :: 4 word) !! 1" by simp
lemma "\<not> (0b0010 :: 4 word) !! 0" by simp
lemma "\<not> (0b1000 :: 3 word) !! 4" by simp

lemma "(0b11000 :: 10 word) !! n = (n = 4 \<or> n = 3)" 
  by (auto simp add: bin_nth_Bit)

lemma "set_bit 55 7 True = (183::'a::len0 word)" by simp
lemma "set_bit 0b0010 7 True = (0b10000010::'a::len0 word)" by simp
lemma "set_bit 0b0010 1 False = (0::'a::len0 word)" by simp

lemma "lsb (0b0101::'a::len word)" by simp
lemma "\<not> lsb (0b1000::'a::len word)" by simp

lemma "\<not> msb (0b0101::4 word)" by simp
lemma   "msb (0b1000::4 word)" by simp

lemma "word_cat (27::4 word) (27::8 word) = (2843::'a::len word)" by simp
lemma "word_cat (0b0011::4 word) (0b1111::6word) = (0b0011001111 :: 10 word)" 
  by simp

lemma "0b1011 << 2 = (0b101100::'a::len0 word)" by simp
lemma "0b1011 >> 2 = (0b10::8 word)" by simp
lemma "0b1011 >>> 2 = (0b10::8 word)" by simp

lemma "slice 3 (0b101111::6 word) = (0b101::3 word)" by simp

lemma "word_rotr 2 0b0110 = (0b1001::4 word)" by simp
lemma "word_rotl 1 0b1110 = (0b1101::4 word)" by simp
lemma "word_roti 2 0b1110 = (0b1011::4 word)" by simp
lemma "word_roti -2 0b0110 = (0b1001::4 word)" by simp

lemma "(x AND 0xff00) OR (x AND 0x00ff) = (x::16 word)"
proof -
  have "(x AND 0xff00) OR (x AND 0x00ff) = x AND (0xff00 OR 0x00ff)"
    by (simp only: word_ao_dist2)
  also have "0xff00 OR 0x00ff = (-1::16 word)"
    by simp
  also have "x AND -1 = x"
    by simp
  finally show ?thesis .
qed

end