Add support for string/sequence update (#4725)

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

2 files changed, 24 insertions, 0 deletions

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)