Fix equation printing #113

doc/systems.rst

@@ -257,7 +257,7 @@ Continuous-time state-space representation
 Lcapy has two state-space representations: `StateSpace` for
 continuous-time linear time-invariant systems and `DTStateSpace` for
 discrete-time linear time-invariant systems.  Both representations
-share many methods and attributes.
+share many methods and attributes, see :ref:`state-space-analysis`.
 
 A state-space object is created from the state matrix, `A`, input
 matrix, `B`, output matrix `C`, and feed-through matrix `D`::

lcapy/equation.py

@@ -5,6 +5,7 @@
 """
 
 from .expr import ExprPrint, ExprMisc, expr
+from .printing import latex
 from sympy import Eq
 
 
@@ -17,6 +18,12 @@ def __init__(self, lhs, rhs):
         self.lhs = expr(lhs)
         self.rhs = expr(rhs)
 
+    @property
+    def _pexpr(self):
+        """Return expression for printing."""
+
+        return self
+
     # TODO, perhaps add canonical, etc.
 
     def __call__(self, arg, **assumptions):
@@ -32,3 +39,13 @@ def symbols(self):
         """Return dictionary of symbols in the equation keyed by name."""
 
         return dict(self.lhs.symbols, **self.rhs.symbols)
+
+    def _repr_latex_(self):
+        """This is used by jupyter notebooks to display an expression using
+        LaTeX markup.  However, this requires mathjax.  If this method
+        is not defined, jupyter falls back on _repr_pretty_ which
+        outputs unicode."""
+
+        # This is called for Expr but not ExprList
+        s = latex(self._pexpr, mode='plain')
+        return "$$%s$$" % s