src/HOL/Nat.ML
changeset 12931 2c0251fada94
parent 12486 0ed8bdd883e0
child 12949 b94843ffc0d1
     1.1 --- a/src/HOL/Nat.ML	Sun Feb 24 21:47:33 2002 +0100
     1.2 +++ b/src/HOL/Nat.ML	Mon Feb 25 10:42:34 2002 +0100
     1.3 @@ -258,6 +258,18 @@
     1.4                                   delsimps [add_0_right]) 1);
     1.5  qed "add_eq_self_zero";
     1.6  
     1.7 +(* a rather special thm needed for arith_tac: m+n = 0 may arise where m or n
     1.8 +contain Suc. This contradiction must be detected. It cannot be detected by
     1.9 +pulling Suc outside because this interferes with simprocs on
    1.10 +numerals. Sigh. *)
    1.11 +
    1.12 +Goal "m ~= 0 ==> m+n ~= (0::nat)";
    1.13 +by(Asm_full_simp_tac 1);
    1.14 +qed "add_not_0_if_left_not_0";
    1.15 +
    1.16 +Goal "n ~= 0 ==> m+n ~= (0::nat)";
    1.17 +by(Asm_full_simp_tac 1);
    1.18 +qed "add_not_0_if_right_not_0";
    1.19  
    1.20  (**** Additional theorems about "less than" ****)
    1.21