Fix negative number parsing in dtype string (issue #80).

changelog.txt

@@ -8,6 +8,7 @@ version 0.4.9
 * Selection of `prefix` for binary and hexadecimal representations.
 * Fix `cumsum` function bug when dealing with sizes bigger than 32 bits (windows) / 64 bits (linux) (issue #76).
 * Fix `numpy.reshape` function handling. This function was returning optimal size instead of same by default (issue #77).
+* Fix negative number parsing in `dtype` string (issue #80).
 
 version 0.4.8
 --------------------------------------------------

fxpmath/__init__.py

@@ -1,4 +1,4 @@
-__version__ = '0.4.9-dev7'
+__version__ = '0.4.9-dev8'
 
 import sys
 import os

fxpmath/objects.py

@@ -316,10 +316,10 @@ def get_dtype(self, notation=None):
         return self._dtype
 
     def _qfmt(self):
-        return re.compile(r'(s|u|q|uq|qu)(\d+)(\.\d+)?')
+        return re.compile(r'(s|u|q|uq|qu)(\d+)(\.[+-]?\d+)?')
 
     def _fxpfmt(self):
-        return re.compile(r'fxp-(s|u)(\d+)/(\d+)(-complex)?')
+        return re.compile(r'fxp-(s|u)(\d+)/([+-]?\d+)(-complex)?')
 
     def _parseformatstr(self, fmt):
         fmt = fmt.casefold()

tests/test_issues.py

@@ -433,3 +433,19 @@ def test_issue_77_v0_4_8():
     y = np.reshape(x, (1, 4))
     # fxp-s4/3-complex
     assert y.signed == True and y.n_word == 5 and y.n_frac == 3
+
+def test_issue_80_v0_4_8():
+    # Creation of Fxp-object with negative n_frac
+
+    # The following code results in unexpected behaviour 
+    # when trying to specify the same type using alternative formats
+    x = Fxp(16, signed=True, n_word=8, n_frac=-2)
+    # -> x.dtype = 'fxp-s8/-2' , ok
+    assert x.dtype == 'fxp-s8/-2'
+
+    x = Fxp(16, dtype='S10.-2')
+    assert x.dtype == 'fxp-s8/-2'
+
+    x = Fxp(16, dtype='fxp-s8/-2')
+    assert x.dtype == 'fxp-s8/-2'
+