From b189292b458335aecdda807368d5d3e22feceb47 Mon Sep 17 00:00:00 2001
From: Nao Pross <np@0hm.ch>
Date: Sun, 5 May 2024 11:29:23 +0200
Subject: Make expressionstate partially backwards compatible

See also 13f11cb60021d4c143ce8c80e9b0c5027a4bf434
---
 polymatrix/expressionstate/mixins.py | 47 ++++++++++++++++++++++++++++++++++--
 1 file changed, 45 insertions(+), 2 deletions(-)

diff --git a/polymatrix/expressionstate/mixins.py b/polymatrix/expressionstate/mixins.py
index 15f5712..e4da232 100644
--- a/polymatrix/expressionstate/mixins.py
+++ b/polymatrix/expressionstate/mixins.py
@@ -2,11 +2,12 @@ from __future__ import annotations
 from typing import TYPE_CHECKING
 
 from abc import abstractmethod
-from typing import NamedTuple, cast
+from typing import NamedTuple, Iterable 
 from math import prod
 import dataclasses
 
 from polymatrix.variable.abc import Variable
+from polymatrix.utils.deprecation import deprecated
 
 from polymatrix.statemonad.mixins import StateCacheMixin
 
@@ -33,7 +34,7 @@ class ExpressionStateMixin(
         """ Map from variable objects to their indices. """
 
     def index(self, var: Variable) -> tuple[ExpressionStateMixin, IndexRange]:
-        """ Get the index range of a variable. """
+        """ Index a variable and get its index range. """
         # Unwrap if wrapped in expression object
         if not isinstance(var, Variable):
             raise ValueError("State can only index object of type Variable!")
@@ -61,6 +62,26 @@ class ExpressionStateMixin(
         state, _ = self.index(var)
         return state
 
+    def get_indices(self, var: Variable) -> Iterable[int]:
+        """
+        Get all indices associated to a variable.
+
+        When a variable is not a scalar multiple indices will be associated to
+        the variables, one for each entry.
+        """
+        if var not in self.indices:
+            raise IndexError(f"There is no variable with index {index}.")
+
+        yield from range(*self.indices[var])
+
+    def get_variable(self, index: int) -> Variable:
+        """ Get the variable object from its index. """
+        for variable, (start, end) in self.indices.items():
+            if start <= index < end:
+                return variable
+
+        raise IndexError(f"There is no variable with index {index}.")
+
     def get_name(self, index: int) -> str:
         """ Get the name of a variable given its index. """
         for variable, (start, end) in self.indices.items():
@@ -72,3 +93,25 @@ class ExpressionStateMixin(
                 return variable.name
 
         raise IndexError(f"There is no variable with index {index}.")
+
+    # -- Old API ---
+
+    @property
+    @deprecated("replaced by n_variables")
+    def n_param(self) -> int:
+        return self.n_variables
+
+    @property
+    @deprecated("replaced by indices")
+    def offset_dict(self):
+        return self.indices
+
+    @property
+    @deprecated("Support for auxillary equations was removed")
+    def auxillary_equations(self):
+        return {}
+
+    @deprecated("replaced by get_variable")
+    def get_key_from_offset(self, index: int) -> Variable:
+        return self.get_variable(index)
+
-- 
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