[Lazy evaluation] Pytato array context transforms

pytato/array.py

@@ -1087,6 +1087,9 @@ def einsum(subscripts: str, *operands: Array) -> Einsum:
     """
     Einstein summation *subscripts* on *operands*.
     """
+
+    from pytato.tags import EinsumInfo
+
     if len(operands) == 0:
         raise ValueError("must specify at least one operand")
 
@@ -1120,6 +1123,7 @@ def einsum(subscripts: str, *operands: Array) -> Einsum:
         access_descriptors.append(access_descriptor)
 
     return Einsum(tuple(access_descriptors), operands,
+                  tags=frozenset([EinsumInfo(subscripts)]),
                   axes=_get_default_axes(len(out_spec)))
 
 # }}}

pytato/tags.py

@@ -97,6 +97,19 @@ class PrefixNamed(_BaseNameTag):
 # }}}
 
 
+# {{{ User operation name
+
+class UserOpInfo(UniqueTag):
+    pass
+
+
+@tag_dataclass
+class EinsumInfo(UserOpInfo):
+    spec: str
+
+# }}}
+
+
 @tag_dataclass
 class AssumeNonNegative(Tag):
     """