Support the SMT-LIB Unicode string standard by default (#4378)

This PR merges --lang=smt2.6.1 and --lang=smt2.6 (default). It makes it so that 2.6 always expects the syntax of the string standard http://smtlib.cs.uiowa.edu/theories-UnicodeStrings.shtml.

I've updated the regressions so that the 2.6 benchmarks are now compliant with the standard. Some of the <=2.5 benchmarks I've updated to 2.6. Others I have left for now, in particular the ones that rely on special characters or ad-hoc escape sequences. The old formats will be supported in the release but removed shortly afterwards.

This PR is a prerequisite for the release, but not necessarily SMT-COMP (which will use --lang=smt2.6.1 if needed). Notice that we still do not have parsing support for str.replace_re or str.replace_re_all. This is required to be fully compliant.

1 files changed, 1 insertions, 1 deletions

diff --git a/test/regress/regress1/fmf/bug723-irrelevant-funs.smt2 b/test/regress/regress1/fmf/bug723-irrelevant-funs.smt2
index b9141f2e2..d700d3b18 100644
--- a/test/regress/regress1/fmf/bug723-irrelevant-funs.smt2
+++ b/test/regress/regress1/fmf/bug723-irrelevant-funs.smt2
@@ -5,7 +5,7 @@
 (define-fun $$isFalse$$ ((b Bool)) Bool (not b))
 (define-fun $$toString$$ ((b Bool)) String (ite b "true" "false"))
 (define-fun $$fromString$$ ((s String)) Bool (= s "true"))
-(define-fun $$inttostr$$ ((i Int)) String (ite (< i 0) (str.++ "-" (int.to.str (- i))) (int.to.str i)))
+(define-fun $$inttostr$$ ((i Int)) String (ite (< i 0) (str.++ "-" (str.from_int (- i))) (str.from_int i)))
 (declare-fun $$takeWhile$$ (String String) String)
 (declare-fun $$takeWhileNot$$ (String String) String)
 (declare-fun $$dropWhile$$ (String String) String)