Add a rewrite for not in

opshin/compiler.py

@@ -18,6 +18,7 @@
 from .rewrite.rewrite_import_uplc_builtins import RewriteImportUPLCBuiltins
 from .rewrite.rewrite_inject_builtins import RewriteInjectBuiltins
 from .rewrite.rewrite_inject_builtin_constr import RewriteInjectBuiltinsConstr
+from .rewrite.rewrite_notin import RewriteNotIn
 from .rewrite.rewrite_orig_name import RewriteOrigName
 from .rewrite.rewrite_remove_type_stuff import RewriteRemoveTypeStuff
 from .rewrite.rewrite_scoping import RewriteScoping
@@ -1012,6 +1013,7 @@ def compile(
         RewriteAugAssign(),
         RewriteComparisonChaining(),
         RewriteTupleAssign(),
+        RewriteNotIn(),
         RewriteImportIntegrityCheck(),
         RewriteImportPlutusData(),
         RewriteImportHashlib(),

opshin/rewrite/rewrite_notin.py

@@ -0,0 +1,21 @@
+from ast import *
+from copy import copy
+
+from ..util import CompilingNodeTransformer
+
+"""
+Rewrites all occurences of (a not in b) into (not (a in b)).
+"""
+
+
+class RewriteNotIn(CompilingNodeTransformer):
+    step = "Rewriting (not in)"
+
+    def visit_Compare(self, node: Compare) -> AST:
+        assert (
+            len(node.ops) == 1
+        ), "RewriteNotIn only works on single comparisons, need to run RewriteComparisonChaining first"
+        if not isinstance(node.ops[0], NotIn):
+            return self.generic_visit(node)
+        new_node = UnaryOp(Not(), Compare(node.left, [In()], node.comparators))
+        return self.generic_visit(new_node)