Use correctly contextualized Decimal loader

Author: kg583

tests/numeric.py

@@ -1,6 +1,6 @@
 import unittest
 
-from decimal import Decimal
+from decimal import Decimal, Overflow
 
 from tivars.types import *
 
@@ -62,6 +62,19 @@ def test_sig_figs(self):
         self.assertEqual(str(TIReal("1.2345678901234e-8")), "1.2345678901234E-8")
         self.assertEqual(str(TIReal("1.2345678901234E88")), "1.2345678901234E88")
 
+        self.assertEqual(str(TIReal(2.675)), "2.675")
+        self.assertEqual(str(TIReal(0.1 + 0.2)), "0.3")
+
+        self.assertEqual(str(TIReal("0009.5")), "9.5")
+        self.assertEqual(str(TIReal("000000000000001")), "1")
+        self.assertEqual(str(TIReal("12345678901234567890")), "1.2345678901234E19")
+
+        with self.assertRaises(Overflow):
+            TIReal(5e300)
+            
+        with self.assertWarns(UserWarning):
+            TIReal(1.8e100)
+
 
 class ComplexTests(unittest.TestCase):
     def complex_float_test(self, comp_type, filename, name, real_sign, real_exponent, real_mantissa,

tivars/numeric.py

@@ -8,8 +8,14 @@
 from .data import *
 
 
-pi = dec.Decimal("3.1415926535898")
-e = dec.Decimal("2.718281828459")
+
+TI_CONTEXT = dec.Context(prec=14, rounding=dec.ROUND_DOWN, Emin=-128, Emax=128, capitals=1)
+"""
+Decimal context for working with TI floats
+"""
+
+pi = TI_CONTEXT.create_decimal("3.1415926535898")
+e = TI_CONTEXT.create_decimal("2.718281828459")
 
 
 def sign(x: int) -> int:
@@ -142,4 +148,4 @@ def set(cls, value: int, *, current: bytes = None, **kwargs) -> bytes:
         return bytes(data)
 
 
-__all__ = ["pi", "e", "sign", "BCD", "LeftNibbleBCD", "RightNibbleBCD"]
+__all__ = ["TI_CONTEXT", "pi", "e", "sign", "BCD", "LeftNibbleBCD", "RightNibbleBCD"]

tivars/types/complex.py

@@ -3,6 +3,7 @@
 """
 
 
+from decimal import InvalidOperation
 from warnings import warn
 
 from tivars.data import *
@@ -317,7 +318,7 @@ def load_string(self, string: str, **kwargs):
         try:
             self.real = self.real_type(parts[0])
 
-        except (TypeError, ValueError):
+        except (InvalidOperation, TypeError, ValueError):
             for type_id, entry_type in self._type_ids.items():
                 if not issubclass(entry_type, RealEntry):
                     continue
@@ -329,7 +330,7 @@ def load_string(self, string: str, **kwargs):
                     self.real = self.get_type(type_id=type_id)(parts[0])
                     break
 
-                except (TypeError, ValueError):
+                except (InvalidOperation, TypeError, ValueError):
                     continue
 
             else:

tivars/types/real.py

@@ -8,6 +8,7 @@
 
 from decimal import Decimal, localcontext
 from fractions import Fraction
+from warnings import warn
 
 from tivars.data import *
 from tivars.models import *
@@ -171,7 +172,7 @@ def load_float(self, decimal: float):
         :param decimal: The float to load
         """
 
-        self.load_decimal(Decimal(decimal))
+        self.load_decimal(Decimal(str(decimal)))
 
     def json_number(self) -> float | str:
         """
@@ -252,36 +253,23 @@ def load_string(self, string: str, **kwargs):
         # Normalize string
         string = replacer(squash(string).upper(), {"~": "-", "|E": "E"})
 
-        if "E" not in string:
-            string += "E0"
+        # Let Decimal handle it
+        self.sign_bit, digits, exponent = TI_CONTEXT.create_decimal(string).as_tuple()
 
-        if "." not in string:
-            string = string.replace("E", ".E")
+        if not isinstance(exponent, int):
+            raise OverflowError("cannot create real number from ±inf")
 
-        neg = string.startswith("-")
-        string = string.strip("+-")
+        elif digits == (0,):
+            self.mantissa = 0
+            self.exponent = 0x80
 
-        # Obtain integer and decimal parts
-        number, exponent = string.split("E")
-        integer, decimal = number.split(".")
-        integer, decimal = integer or "0", decimal or "0"
-
-        if int(integer) == int(decimal) == 0:
-            self.mantissa, self.exponent, self.sign_bit = 0, 0x80, neg
-            return
-
-        # Adjust exponent to make integer mantissa
-        exponent = int(exponent or "0")
-        while not 0 < (value := int(integer)) < 10:
-            if value == 0:
-                integer, decimal = decimal[0], decimal[1:]
-                exponent -= 1
-
-            else:
-                integer, decimal = integer[:-1], integer[-1] + decimal
-                exponent += 1
+        else:
+            self.mantissa = int("".join(map(str, digits)).ljust(14, "0"))
+            self.exponent = exponent + (len(digits) - 1) + 0x80
 
-        self.mantissa, self.exponent, self.sign_bit = int((integer + decimal).ljust(14, "0")[:14]), exponent + 0x80, neg
+        if self.exponent < -29 or 227 < self.exponent:
+            warn(f"Values with |exponent| > 99 raise errors when used for arithmetic.",
+                 UserWarning)
 
 
 class TIUndefinedReal(TIReal, register=True):
@@ -326,7 +314,7 @@ def __format__(self, format_spec: str) -> str:
     def load_fraction(self, fraction: Fraction):
         with localcontext() as ctx:
             ctx.prec = 14
-            decimal = Decimal(fraction.numerator) / fraction.denominator
+            decimal = TI_CONTEXT.create_decimal(fraction.numerator) / fraction.denominator
 
         super().load_string(str(decimal))