added Decimal curriculum (#280)

* added decimal curricula

* added chain sum decimal curriculum

* register DecimalArithmeticCurriculum & DecimalChainSumCurriculum

---------

Co-authored-by: Andreas Koepf <andreas.koepf@provisio.com>

reasoning_gym/arithmetic/decimal_chain_sum.py

@@ -3,6 +3,7 @@ from dataclasses import dataclass
 from decimal import Decimal, InvalidOperation
 from typing import Any, Optional
 
+from ..coaching import AttributeType, BaseCurriculum, RangeAttributeDefinition
 from ..factory import ProceduralDataset, register_dataset
 
 
@@ -160,4 +161,43 @@ class DecimalChainSumDataset(ProceduralDataset):
         return 0.0
 
 
-register_dataset("decimal_chain_sum", DecimalChainSumDataset, DecimalChainSumConfig)
+class DecimalChainSumCurriculum(BaseCurriculum):
+    def __init__(self):
+        super().__init__(DecimalChainSumCurriculum.__name__, DecimalChainSumConfig)
+
+        # Define attributes
+        self._define_attributes(
+            RangeAttributeDefinition(
+                name="num_terms",
+                levels=[2, 3, 4, 5],
+                default_level=0,
+                description="Maximum number of terms in the expression",
+                attr_type=AttributeType.APPEND,
+                min_value=2,
+                lower_field_name="min_terms",
+                upper_field_name="max_terms",
+            ),
+            RangeAttributeDefinition(
+                name="num_digits",
+                levels=[1, 2, 4, 10],
+                default_level=0,  # Start with 1-digit numbers
+                description="Number of digits in each operand",
+                attr_type=AttributeType.APPEND,
+                min_value=1,
+                lower_field_name="min_digits",
+                upper_field_name="max_digits",
+            ),
+            RangeAttributeDefinition(
+                name="decimal_places",
+                levels=[1, 2, 3, 4],
+                default_level=0,
+                description="Number of decimal places in each operand",
+                attr_type=AttributeType.APPEND,
+                min_value=1,
+                lower_field_name="min_decimal_places",
+                upper_field_name="max_decimal_places",
+            ),
+        )
+
+
+register_dataset("decimal_chain_sum", DecimalChainSumDataset, DecimalChainSumConfig, DecimalChainSumCurriculum)