Require capitalizing NaN and Inf like so

NEWS

@@ -8,6 +8,7 @@ Changes from 0.13.0
    * The compiler now automatically promotes values to Hy model objects
      as necessary, so you can write ``(eval `(+ 1 ~n))`` instead of
      ``(eval `(+ 1 ~(HyInteger n)))``
+   * Literal `Inf`s and `NaN`s must now be capitalized like that
 
    [ Bug Fixes ]
    * Numeric literals are no longer parsed as symbols when followed by a dot

docs/language/api.rst

@@ -52,6 +52,9 @@ digits.
 
     (print 10,000,000,000 10_000_000_000)
 
+Unlike Python, Hy provides literal forms for NaN and infinity: `NaN`, `Inf`,
+and `-Inf`.
+
 string literals
 ---------------
 

hy/models.py

@@ -3,6 +3,7 @@
 # license. See the LICENSE.
 
 from __future__ import unicode_literals
+from math import isnan, isinf
 from hy._compat import PY3, str_type, bytes_type, long_type, string_types
 from fractions import Fraction
 
@@ -142,15 +143,24 @@ if not PY3:  # do not add long on python3
     _wrappers[long_type] = HyInteger
 
 
+def check_inf_nan_cap(arg, value):
+    if isinstance(arg, string_types):
+        if isinf(value) and "Inf" not in arg:
+            raise ValueError('Inf must be capitalized as "Inf"')
+        if isnan(value) and "NaN" not in arg:
+            raise ValueError('NaN must be capitalized as "NaN"')
+
+
 class HyFloat(HyObject, float):
     """
     Internal representation of a Hy Float. May raise a ValueError as if
     float(foo) was called, given HyFloat(foo).
     """
 
-    def __new__(cls, number, *args, **kwargs):
+    def __new__(cls, num, *args, **kwargs):
-        number = float(strip_digit_separators(number))
+        value = super(HyFloat, cls).__new__(cls, strip_digit_separators(num))
-        return super(HyFloat, cls).__new__(cls, number)
+        check_inf_nan_cap(num, value)
+        return value
 
 _wrappers[float] = HyFloat
 
@@ -161,9 +171,18 @@ class HyComplex(HyObject, complex):
     complex(foo) was called, given HyComplex(foo).
     """
 
-    def __new__(cls, number, *args, **kwargs):
+    def __new__(cls, num, *args, **kwargs):
-        number = complex(strip_digit_separators(number))
+        value = super(HyComplex, cls).__new__(cls, strip_digit_separators(num))
-        return super(HyComplex, cls).__new__(cls, number)
+        if isinstance(num, string_types):
+            p1, _, p2 = num.lstrip("+-").replace("-", "+").partition("+")
+            if p2:
+                check_inf_nan_cap(p1, value.real)
+                check_inf_nan_cap(p2, value.imag)
+            elif "j" in p1:
+                check_inf_nan_cap(p1, value.imag)
+            else:
+                check_inf_nan_cap(p1, value.real)
+        return value
 
 _wrappers[complex] = HyComplex
 

tests/test_lex.py

@@ -2,6 +2,7 @@
 # This file is part of Hy, which is free software licensed under the Expat
 # license. See the LICENSE.
 
+from math import isnan
 from hy.models import (HyExpression, HyInteger, HyFloat, HyComplex, HySymbol,
                        HyString, HyDict, HyList, HySet, HyCons)
 from hy.lex import LexException, PrematureEndOfInput, tokenize
@@ -91,6 +92,22 @@ def test_lex_expression_float():
     assert objs == [HyExpression([HySymbol("foo"), HyFloat(1.e7)])]
 
 
+def test_lex_nan_and_inf():
+
+    assert isnan(tokenize("NaN")[0])
+    assert tokenize("Nan") == [HySymbol("Nan")]
+    assert tokenize("nan") == [HySymbol("nan")]
+    assert tokenize("NAN") == [HySymbol("NAN")]
+
+    assert tokenize("Inf") == [HyFloat(float("inf"))]
+    assert tokenize("inf") == [HySymbol("inf")]
+    assert tokenize("INF") == [HySymbol("INF")]
+
+    assert tokenize("-Inf") == [HyFloat(float("-inf"))]
+    assert tokenize("-inf") == [HySymbol("_inf")]
+    assert tokenize("-INF") == [HySymbol("_INF")]
+
+
 def test_lex_expression_complex():
     """ Make sure expressions can produce complex """
 
@@ -102,6 +119,11 @@ def test_lex_expression_complex():
     assert t("-0.5j") == f(HyComplex(-0.5j))
     assert t("1.e7j") == f(HyComplex(1e7j))
     assert t("j") == f(HySymbol("j"))
+    assert isnan(t("NaNj")[0][1].imag)
+    assert t("nanj") == f(HySymbol("nanj"))
+    assert t("Inf+Infj") == f(HyComplex(complex(float("inf"), float("inf"))))
+    assert t("Inf-Infj") == f(HyComplex(complex(float("inf"), float("-inf"))))
+    assert t("Inf-INFj") == f(HySymbol("Inf_INFj"))
 
 
 def test_lex_digit_separators():