Add support for string/sequence update (#4725)

This adds basic support for string/sequence updating, which has a semantics that is length preserving.

5 files changed, 45 insertions, 0 deletions

diff --git a/test/regress/CMakeLists.txt b/test/regress/CMakeLists.txt
index dd48b1fff..c5048ae63 100644
--- a/test/regress/CMakeLists.txt
+++ b/test/regress/CMakeLists.txt
@@ -1871,6 +1871,8 @@ set(regress_1_tests
   regress1/strings/timeout-no-resp.smt2
   regress1/strings/type002.smt2
   regress1/strings/type003.smt2
+  regress1/strings/update-ex1.smt2
+  regress1/strings/update-ex2.smt2
   regress1/strings/username_checker_min.smt2
   regress1/sygus-abduct-ex1-grammar.smt2
   regress1/sygus-abduct-test.smt2
@@ -2113,6 +2115,8 @@ set(regress_2_tests
   regress2/strings/replaceall-diffrange.smt2
   regress2/strings/replaceall-len-c.smt2
   regress2/strings/small-1.smt2
+  regress2/strings/update-ex3.smt2
+  regress2/strings/update-ex4-seq.smt2
   regress2/sygus/DRAGON_1.lus.sy
   regress2/sygus/MPwL_d1s3.sy
   regress2/sygus/array_sum_dd.sy
diff --git a/test/regress/regress1/strings/update-ex1.smt2 b/test/regress/regress1/strings/update-ex1.smt2
new file mode 100644
index 000000000..deff4b6c2
--- /dev/null
+++ b/test/regress/regress1/strings/update-ex1.smt2
@@ -0,0 +1,8 @@
+(set-logic QF_SLIA)
+(set-option :strings-exp true)
+(set-info :status sat)
+(declare-fun s () String)
+
+(assert (not (= (str.substr (str.update "AAAAAA" 1 s) 5 1) "A")))
+
+(check-sat)
diff --git a/test/regress/regress1/strings/update-ex2.smt2 b/test/regress/regress1/strings/update-ex2.smt2
new file mode 100644
index 000000000..dedba68b2
--- /dev/null
+++ b/test/regress/regress1/strings/update-ex2.smt2
@@ -0,0 +1,9 @@
+(set-logic QF_SLIA)
+(set-option :strings-exp true)
+(set-info :status unsat)
+(declare-fun s () String)
+
+(assert (not (= (str.substr (str.update "AAAAAA" 1 s) 5 1) "A")))
+(assert (< (str.len s) 3))
+
+(check-sat)
diff --git a/test/regress/regress2/strings/update-ex3.smt2 b/test/regress/regress2/strings/update-ex3.smt2
new file mode 100644
index 000000000..e21a2f445
--- /dev/null
+++ b/test/regress/regress2/strings/update-ex3.smt2
@@ -0,0 +1,13 @@
+(set-logic QF_SLIA)
+(set-option :strings-exp true)
+(set-info :status sat)
+(declare-fun s () String)
+(declare-fun x () Int)
+(declare-fun y () Int)
+
+(assert (= s (str.update (str.update "ABCDEFG" x "ZZZ") y "X")))
+(assert (not (str.contains s "B")))
+(assert (not (str.contains s "D")))
+(assert (not (str.contains s "G")))
+
+(check-sat)
diff --git a/test/regress/regress2/strings/update-ex4-seq.smt2 b/test/regress/regress2/strings/update-ex4-seq.smt2
new file mode 100644
index 000000000..d28df8534
--- /dev/null
+++ b/test/regress/regress2/strings/update-ex4-seq.smt2
@@ -0,0 +1,11 @@
+(set-logic QF_SLIA)
+(set-option :strings-exp true)
+(set-info :status sat)
+(declare-fun s () (Seq Int))
+(declare-fun x () Int)
+
+(assert (= s (seq.++ (seq.unit 0) (seq.unit 1) (seq.unit 7) (seq.unit 3) (seq.unit 4) (seq.unit 5))))
+
+(assert (not (= s (seq.update s x (seq.unit x)))))
+
+(check-sat)