Feature/nan zero sign (#153)

CHANGELOG.rst

@@ -106,6 +106,19 @@ Fixed
   Now all ``Decimal`` inputs are immediately normalized before any
   formatting.
   [`#148 <https://github.com/jagerber48/sciform/issues/148>`_]
+* Fixed the behavior around the sign symbols for zero and non-finite
+  inputs.
+  Previously ``0`` was treated as positive for the sake of resolving
+  its sign symbol, the sign of infinite numbers was preserved but
+  ``+inf`` did not respect the ``"+"`` and ``" "`` sign modes, and
+  ``nan`` never had a sign but also never had an extra character added
+  for ``"+"`` or ``" "`` sign modes.
+  Now both ``0`` and ``nan`` are treated as having no sign.
+  In both ``"+"`` and ``" "`` sign modes ``0`` and ``nan`` are prepended
+  by a space.
+  The sign of infinite numbers is retained as before, but now formatting
+  of these numbers respects the sign mode.
+  [`#147 <https://github.com/jagerber48/sciform/issues/147>`_]
 
 ----
 

docs/source/options.rst

@@ -502,7 +502,6 @@ extra whitespace in place of a sign symbol.
 This mode may be useful to match string lengths when positive and
 negatives numbers are being presented together, but without explicitly
 including a ``'+'`` symbol.
-Note that ``0`` is always considered positive.
 
 >>> formatter = Formatter(sign_mode="-")
 >>> print(formatter(42))
@@ -514,6 +513,37 @@ Note that ``0`` is always considered positive.
 >>> print(formatter(42))
  42
 
+Note that both :class:`float` ``nan`` and :class:`float` ``0`` have sign
+bits which may be positive or negative.
+:mod:`sciform` always ignores these sign bits and never puts a ``+`` or
+``-`` symbol in front of either ``nan`` or ``0``.
+In ``"+"`` or ``" "`` sign modes ``nan`` and ``0`` are always preceded
+by a space.
+The sign symbol for ``±inf`` is resolved the same as for
+finite numbers.
+
+>>> formatter = Formatter(sign_mode="-")
+>>> print(formatter(float("-0")))
+0
+>>> print(formatter(float("-nan")))
+nan
+>>> print(formatter(float("+inf")))
+inf
+>>> formatter = Formatter(sign_mode="+")
+>>> print(formatter(float("+0")))
+ 0
+>>> print(formatter(float("+nan")))
+ nan
+>>> print(formatter(float("+inf")))
++inf
+>>> formatter = Formatter(sign_mode=" ")
+>>> print(formatter(float("-0")))
+ 0
+>>> print(formatter(float("-nan")))
+ nan
+>>> print(formatter(float("-inf")))
+-inf
+
 Capitalization
 ==============
 

docs/source/usage.rst

@@ -130,7 +130,7 @@ types for the uncertainty.
 
 These example strings can be natively cast to numeric types like
 :class:`int`, :class:`float`, or :class:`Decimal`.
-However, the :class:`Formatter` and :class:`SciNum` also accept
+However, :class:`Formatter` and :class:`SciNum` also accept
 formatted strings which contain the numeric information, but with more
 sophisticated formatting.
 

src/sciform/format_utils.py

@@ -234,16 +234,26 @@ def get_exp_str(  # noqa: PLR0913
 def get_sign_str(num: Decimal, sign_mode: SignModeEnum) -> str:
     """Get the format sign string."""
     if num < 0:
+        # Always return "-" for negative numbers.
         sign_str = "-"
-    elif sign_mode is SignModeEnum.ALWAYS:
-        sign_str = "+"
-    elif sign_mode is SignModeEnum.SPACE:
+    elif num > 0:
+        # Return "+", " ", or "" for positive numbers.
+        if sign_mode is SignModeEnum.ALWAYS:
+            sign_str = "+"
+        elif sign_mode is SignModeEnum.SPACE:
+            sign_str = " "
+        elif sign_mode is SignModeEnum.NEGATIVE:
+            sign_str = ""
+        else:
+            msg = f"Invalid sign mode {sign_mode}."
+            raise ValueError(msg)
+    elif sign_mode is SignModeEnum.ALWAYS or sign_mode is SignModeEnum.SPACE:
+        # For anything else (typically 0, possibly nan) return " " in "+" and " " modes
         sign_str = " "
-    elif sign_mode is SignModeEnum.NEGATIVE:
-        sign_str = ""
     else:
-        msg = f"Invalid sign mode {sign_mode}."
-        raise ValueError(msg)
+        # Otherwise return the empty string.
+        sign_str = ""
+
     return sign_str
 
 

src/sciform/formatting.py

@@ -16,6 +16,7 @@
     get_exp_str,
     get_mantissa_exp_base,
     get_round_digit,
+    get_sign_str,
     get_val_unc_exp,
     get_val_unc_mantissa_strs,
     get_val_unc_top_digit,
@@ -66,10 +67,12 @@ def format_non_finite(num: Decimal, options: FinalizedOptions) -> str:
     """Format non-finite numbers."""
     if num.is_nan():
         num_str = "nan"
-    elif num == Decimal("inf"):
+        if options.sign_mode in [SignModeEnum.ALWAYS, SignModeEnum.SPACE]:
+            num_str = f" {num_str}"
+    elif num.is_infinite():
         num_str = "inf"
-    elif num == Decimal("-inf"):
-        num_str = "-inf"
+        sign_str = get_sign_str(num, options.sign_mode)
+        num_str = f"{sign_str}{num_str}"
     else:
         msg = f"format_non_finite() cannot format {num}."
         raise ValueError(msg)

tests/test_float_formatter.py

@@ -128,12 +128,73 @@ def test_nan(self):
             (
                 float("nan"),
                 [
+                    (Formatter(sign_mode="-"), "nan"),
+                    (Formatter(sign_mode="+"), " nan"),
+                    (Formatter(sign_mode=" "), " nan"),
                     (Formatter(exp_mode="percent"), "nan"),
                     (Formatter(exp_mode="percent", nan_inf_exp=True), "(nan)%"),
                 ],
             ),
+            (
+                float("-nan"),
+                [
+                    (Formatter(sign_mode="-"), "nan"),
+                    (Formatter(sign_mode="+"), " nan"),
+                    (Formatter(sign_mode=" "), " nan"),
+                    (Formatter(exp_mode="percent"), "nan"),
+                    (Formatter(exp_mode="percent", nan_inf_exp=True), "(nan)%"),
+                ],
+            ),
+        ]
+
+        self.run_float_formatter_cases(cases_list)
+
+    def test_inf(self):
+        cases_list = [
+            (
+                float("inf"),
+                [
+                    (Formatter(sign_mode="-"), "inf"),
+                    (Formatter(sign_mode="+"), "+inf"),
+                    (Formatter(sign_mode=" "), " inf"),
+                    (Formatter(exp_mode="percent", nan_inf_exp=False), "inf"),
+                    (Formatter(exp_mode="percent", nan_inf_exp=True), "(inf)%"),
+                ],
+            ),
+            (
+                float("-inf"),
+                [
+                    (Formatter(sign_mode="-"), "-inf"),
+                    (Formatter(sign_mode="+"), "-inf"),
+                    (Formatter(sign_mode=" "), "-inf"),
+                    (Formatter(exp_mode="percent", nan_inf_exp=False), "-inf"),
+                    (Formatter(exp_mode="percent", nan_inf_exp=True), "(-inf)%"),
+                ],
+            ),
         ]
+        self.run_float_formatter_cases(cases_list)
 
+    def test_zero(self):
+        cases_list = [
+            (
+                float("+0"),
+                [
+                    (Formatter(sign_mode="-"), "0"),
+                    (Formatter(sign_mode="+"), " 0"),
+                    (Formatter(sign_mode=" "), " 0"),
+                    (Formatter(exp_mode="percent", nan_inf_exp=False), "0%"),
+                ],
+            ),
+            (
+                float("-0"),
+                [
+                    (Formatter(sign_mode="-"), "0"),
+                    (Formatter(sign_mode="+"), " 0"),
+                    (Formatter(sign_mode=" "), " 0"),
+                    (Formatter(exp_mode="percent", nan_inf_exp=False), "0%"),
+                ],
+            ),
+        ]
         self.run_float_formatter_cases(cases_list)
 
     def test_parts_per_exp(self):

tests/test_float_fsml.py

@@ -529,7 +529,7 @@ def test_signs(self):
                 [
                     ("", "0"),
                     ("-", "0"),
-                    ("+", "+0"),
+                    ("+", " 0"),
                     (" ", " 0"),
                 ],
             ),
@@ -538,7 +538,7 @@ def test_signs(self):
                 [
                     ("", "0"),
                     ("-", "0"),
-                    ("+", "+0"),
+                    ("+", " 0"),
                     (" ", " 0"),
                 ],
             ),