Assign value to a bitvector (SMTLIB2, Z3)?

I am using Z3 version 3.0. I want to assign a value to a bitvector variable, like below. But Z3 reports error "invalid function application, sort mismatch on a开发者_Python百科rgument at position 2 in line 3".

It seems wrong with my constant #x0a? how can i fix this?

Thanks

(set-logic QF_BV)
(declare-fun a () (_ BitVec 32))
(assert (= a #x0a))
(check-sat)

In the SMT-LIB 2.0 standard, #x0a is a bitvector of size 8. You get the sort mismatch error because the constant a is a bitvector of size 32. You can avoid the type/sort error message by rewriting your example as:

(set-logic QF_BV)
(declare-fun a () (_ BitVec 32))
(assert (= a #x0000000a))
(check-sat)

SMT-LIB also supports bitvector literals of the form (_ bv[num] [size]), where [num] is in decimal notation, and [size] is the size of the bitvector. Thus, you can also write the bitvector literal #x0000000a as (_ bv10 32).

BTW, SMT-LIB also supports bitvector literals in binary notation. For example, #b010 is a bitvector of size 3.