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decl and rewriter for string StartsWith

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This commit is contained in:
Murphy Berzish 2016-06-13 22:27:46 -04:00
parent be5cc02a45
commit 7d8e54c50f
4 changed files with 38 additions and 16 deletions
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41
src/ast/rewriter/str_rewriter.cpp
View file

@ -42,24 +42,30 @@ br_status str_rewriter::mk_str_CharAt(expr * arg0, expr * arg1, expr_ref & resul
result = m_strutil.mk_string(resultStr);
return BR_DONE;
} else {
// TODO if we ever figure out how to assert axioms in here, add this code
// TODO if we ever figure out how to assert axioms in here, add the axiom code from Z3str2's strAstReduce.cpp
return BR_FAILED;
/*
Z3_ast ts0 = my_mk_internal_string_var(t);
Z3_ast ts1 = my_mk_internal_string_var(t);
Z3_ast ts2 = my_mk_internal_string_var(t);
}
}
Z3_ast cond = mk_2_and(t, Z3_mk_ge(ctx, args[1], mk_int(ctx, 0)), Z3_mk_lt(ctx, args[1], mk_length(t, args[0])));
Z3_ast and_item[3];
and_item[0] = Z3_mk_eq(ctx, args[0], mk_concat(t, ts0, mk_concat(t, ts1, ts2)));
and_item[1] = Z3_mk_eq(ctx, args[1], mk_length(t, ts0));
and_item[2] = Z3_mk_eq(ctx, mk_length(t, ts1), mk_int(ctx, 1));
Z3_ast thenBranch = Z3_mk_and(ctx, 3, and_item);
Z3_ast elseBranch = Z3_mk_eq(ctx, ts1, my_mk_str_value(t, ""));
breakdownAssert = Z3_mk_ite(ctx, cond, thenBranch, elseBranch);
return ts1;
*/
br_status str_rewriter::mk_str_StartsWith(expr * haystack, expr * needle, expr_ref & result) {
TRACE("t_str_rw", tout << "rewrite (StartsWith " << mk_pp(haystack, m()) << " " << mk_pp(needle, m()) << ")" << std::endl;);
if (m_strutil.is_string(haystack) && m_strutil.is_string(needle)) {
TRACE("t_str_rw", tout << "evaluating constant StartsWith predicate" << std::endl;);
std::string haystackStr = m_strutil.get_string_constant_value(haystack);
std::string needleStr = m_strutil.get_string_constant_value(needle);
if (haystackStr.length() < needleStr.length()) {
result = m().mk_false();
return BR_DONE;
} else {
if (haystackStr.substr(0, needleStr.length()) == needleStr) {
result = m().mk_true();
} else {
result = m().mk_false();
}
return BR_DONE;
}
} else {
return BR_FAILED;
}
}
@ -73,6 +79,9 @@ br_status str_rewriter::mk_app_core(func_decl * f, unsigned num_args, expr * con
case OP_STR_CHARAT:
SASSERT(num_args == 2);
return mk_str_CharAt(args[0], args[1], result);
case OP_STR_STARTSWITH:
SASSERT(num_args == 2);
return mk_str_StartsWith(args[0], args[1], result);
default:
return BR_FAILED;
}

1
src/ast/rewriter/str_rewriter.h
View file

@ -41,6 +41,7 @@ public:
br_status mk_eq_core(expr * lhs, expr * rhs, expr_ref & result);
br_status mk_str_CharAt(expr * arg0, expr * arg1, expr_ref & result);
br_status mk_str_StartsWith(expr * haystack, expr * needle, expr_ref & result);
bool reduce_eq(expr * l, expr * r, expr_ref_vector & lhs, expr_ref_vector & rhs, bool & change);
bool reduce_eq(expr_ref_vector& ls, expr_ref_vector& rs, expr_ref_vector& lhs, expr_ref_vector& rhs, bool& change);