[Kinetics] Add access to reactant and product strings

In C++, these are the reactantString() and productString() methods.  In Python,
these are the 'reactants' and 'products' properties.

Resolves Issue 110.

include/cantera/kinetics/GasKinetics.h

@@ -112,6 +112,14 @@ public:
         return m_rxneqn[i];
     }
 
+    virtual std::string reactantString(size_t i) const {
+        return m_reactantStrings[i];
+    }
+
+    virtual std::string productString(size_t i) const {
+        return m_productStrings[i];
+    }
+
     virtual bool isReversible(size_t i) {
         if (std::find(m_revindex.begin(), m_revindex.end(), i)
                 < m_revindex.end()) {
@@ -200,6 +208,8 @@ protected:
     std::vector<size_t> m_revindex;
 
     std::vector<std::string> m_rxneqn;
+    std::vector<std::string> m_reactantStrings;
+    std::vector<std::string> m_productStrings;
 
     //! @name Reaction rate data
     //!@{

include/cantera/kinetics/Kinetics.h

@@ -700,6 +700,16 @@ public:
         throw NotImplementedError("Kinetics::reactionStd::String");
     }
 
+    //! Returns a string containing the reactants side of the reaction equation.
+    virtual std::string reactantString(size_t i) const {
+        throw NotImplementedError("Kinetics::reactionString");
+    }
+
+    //! Returns a string containing the products side of the reaction equation.
+    virtual std::string productString(size_t i) const {
+        throw NotImplementedError("Kinetics::productString");
+    }
+
     /**
      * Return the forward rate constants
      *

include/cantera/kinetics/ReactionData.h

@@ -108,6 +108,12 @@ public:
     //! The reaction equation. Used only for display purposes.
     std::string equation;
 
+    //! The reactants half of the reaction equation, used for display purposes.
+    std::string reactantString;
+
+    //! The products half of the reaction equation, used for display purposes.
+    std::string productString;
+
     //! The default third body efficiency for species not listed in
     //! #thirdBodyEfficiencies.
     doublereal default_3b_eff;

interfaces/cython/cantera/_cantera.pxd

@@ -165,6 +165,8 @@ cdef extern from "cantera/kinetics/Kinetics.h" namespace "Cantera":
         cbool isReversible(int) except +
         int reactionType(int) except +
         string reactionString(int) except +
+        string reactantString(int) except +
+        string productString(int) except +
         double reactantStoichCoeff(int, int) except +
         double productStoichCoeff(int, int) except +
 

interfaces/cython/cantera/kinetics.pyx

@@ -104,6 +104,16 @@ cdef class Kinetics(_SolutionBase):
         self._check_reaction_index(i_reaction)
         return pystr(self.kinetics.reactionString(i_reaction))
 
+    def reactants(self, int i_reaction):
+        """The reactants portion of the reaction equation"""
+        self._check_reaction_index(i_reaction)
+        return pystr(self.kinetics.reactantString(i_reaction))
+
+    def products(self, int i_reaction):
+        """The products portion of the reaction equation"""
+        self._check_reaction_index(i_reaction)
+        return pystr(self.kinetics.productString(i_reaction))
+
     def reaction_equations(self, indices=None):
         """
         Returns a list containing the reaction equation for all reactions in the

interfaces/cython/cantera/test/test_kinetics.py

@@ -62,6 +62,18 @@ class TestKinetics(utilities.CanteraTest):
         self.assertEqual(self.phase.reaction_equation(16),
                          'H + H2O2 <=> HO2 + H2')
 
+    def test_reactants_products(self):
+        for i in range(self.phase.n_reactions):
+            R = self.phase.reactants(i)
+            P = self.phase.products(i)
+            self.assertTrue(self.phase.reaction_equation(i).startswith(R))
+            self.assertTrue(self.phase.reaction_equation(i).endswith(P))
+            for k in range(self.phase.n_species):
+                if self.phase.reactant_stoich_coeff(k,i) != 0:
+                    self.assertIn(self.phase.species_name(k), R)
+                if self.phase.product_stoich_coeff(k,i) != 0:
+                    self.assertIn(self.phase.species_name(k), P)
+
     def test_stoich_coeffs(self):
         nu_r = self.phase.reactant_stoich_coeffs()
         nu_p = self.phase.product_stoich_coeffs()

src/kinetics/GasKinetics.cpp

@@ -87,6 +87,8 @@ GasKinetics& GasKinetics::operator=(const GasKinetics& right)
     m_dn = right.m_dn;
     m_revindex = right.m_revindex;
     m_rxneqn = right.m_rxneqn;
+    m_reactantStrings = right.m_reactantStrings;
+    m_productStrings = right.m_productStrings;
 
     m_logp_ref = right.m_logp_ref;
     m_logc_ref  = right.m_logc_ref;
@@ -505,6 +507,8 @@ void GasKinetics::addReaction(ReactionData& r)
     installGroups(reactionNumber(), r.rgroups, r.pgroups);
     incrementRxnCount();
     m_rxneqn.push_back(r.equation);
+    m_reactantStrings.push_back(r.reactantString);
+    m_productStrings.push_back(r.productString);
     m_rxntype.push_back(r.reactionType);
 }
 

src/kinetics/importKinetics.cpp

@@ -628,13 +628,18 @@ bool rxninfo::installReaction(int iRxn, const XML_Node& r, Kinetics& kin,
     // string representation. Post-process to convert "[" and "]" characters
     // back into "<" and ">" which cannot easily be stored in an XML file. This
     // reaction string is used only for display purposes. It is not parsed for
-    //  the identities of reactants or products.
+    // the identities of reactants or products.
     rdata.equation = (r.hasChild("equation")) ? r("equation") : "<no equation>";
-    for (size_t nn = 0; nn < rdata.equation.size(); nn++) {
-        if (rdata.equation[nn] == '[') {
-            rdata.equation[nn] = '<';
-        } else if (rdata.equation[nn] == ']') {
-            rdata.equation[nn] = '>';
+    static const char* delimiters[] = {" [=] ", " =] ", " = ", "[=]", "=]", "="};
+    static const char* replacements[] = {" <=> ", " => ", " = ", "<=>", "=>", "="};
+    for (size_t i = 0; i < 6; i++) {
+        size_t n = rdata.equation.find(delimiters[i]);
+        if (n != npos) {
+            size_t w = strlen(delimiters[i]);
+            rdata.reactantString = stripws(rdata.equation.substr(0, n));
+            rdata.productString = stripws(rdata.equation.substr(n+w, npos));
+            rdata.equation.replace(n, w, replacements[i]);
+            break;
         }
     }