refactor: Inherit ChainSum from ProceduralDataset base class

reasoning_gym/arithmetic/chain_sum.py

@@ -1,6 +1,7 @@
 import random
 from dataclasses import dataclass
 from typing import Optional
+from ..dataset import ProceduralDataset
 
 
 @dataclass
@@ -27,17 +28,13 @@ class ChainSumConfig:
             assert 10 ** (self.min_digits - 1) >= 1, "min_digits would result in invalid number range"
 
 
-class ChainSum:
+class ChainSum(ProceduralDataset):
     """Generates simple arithmetic tasks using only + and - operators"""
 
     def __init__(self, config: ChainSumConfig):
         self.config = config
         self.config.validate()
-        # Generate base seed if none provided
-        self.seed = config.seed if config.seed is not None else random.randint(0, 2**32)
-
-    def __len__(self) -> int:
-        return self.config.size
+        super().__init__(seed=config.seed, size=config.size)
 
     def __getitem__(self, idx: int) -> dict:
         """Generate a single chain sum task
@@ -73,18 +70,6 @@ class ChainSum:
             },
         }
 
-    def __iter__(self):
-        """Make the dataset iterable"""
-        self._current_idx = 0
-        return self
-
-    def __next__(self):
-        """Get next item in iteration"""
-        if self._current_idx >= self.config.size:
-            raise StopIteration
-        item = self[self._current_idx]
-        self._current_idx += 1
-        return item
 
     def _generate_task(self, rng: random.Random, num_terms: int, min_value: int, max_value: int) -> tuple[str, int]:
         """Generate a chain sum task