Update Ubuntu job name in Azure pipeline and add string variable creation in C API example

azure-pipelines.yml

@@ -99,7 +99,7 @@ jobs:
     - template: scripts/generate-doc.yml
 
 
-- job: "Ubuntu20OCamlStatic"
+- job: "UbuntuOCamlStatic"
   displayName: "Ubuntu with OCaml on z3-static"
   pool:
     vmImage: "Ubuntu-latest"

examples/c/test_capi.c

@@ -165,6 +165,15 @@ Z3_ast mk_int_var(Z3_context ctx, const char * name)
     return mk_var(ctx, name, ty);
 }
 
+/**
+   \brief Create a string variable using the given name.
+*/
+Z3_ast mk_string_var(Z3_context ctx, const char * name)
+{
+    Z3_sort ty = Z3_mk_string_sort(ctx);
+    return mk_var(ctx, name, ty);
+}
+
 /**
    \brief Create a Z3 integer node using a C int.
 */
@@ -1615,7 +1624,7 @@ void error_code_example2() {
         Z3_del_config(cfg);
 
         x   = mk_int_var(ctx, "x");
-        y   = mk_bool_var(ctx, "y");
+        y   = mk_string_var(ctx, "y");
         printf("before Z3_mk_iff\n");
         /* the next call will produce an error */
         app = Z3_mk_iff(ctx, x, y);