Add latex representation of Units

.gitignore

@@ -5,3 +5,5 @@
 build/
 dist/
 pyqn.egg-info/
+.venv
+activate

pyqn/units.py

@@ -223,6 +223,21 @@ def html(self):
                 h.append(' ')
         return ''.join(h)
 
+
+    @property
+    def latex(self):
+        e = []
+        n = len(self.atom_units)
+        for i, atom_unit in enumerate(self.atom_units):
+            # TODO use proper LaTeX for prefix.
+            e.extend([atom_unit.prefix or '', atom_unit.base_unit.latex])
+            if atom_unit.exponent != 1:
+                e.append('^{' + str(atom_unit.exponent) + '}')
+            if i < n-1:
+                e.append(r'\,')
+        return r'\mathrm{' + ''.join(e) + '}'
+
+
     def conversion(self, other, force=None, strict=False):
         """
         Return the factor required to convert this Units to

setup.py

@@ -1,7 +1,7 @@
 from setuptools import setup, find_packages
 setup(
     name = 'pyqn',
-    version = '1.2',
+    version = '1.2.1',
     packages = find_packages(),
     author = 'Christian Hill',
     url = 'https://github.com/xnx/pyqn',