[Func1] Add Log1

include/cantera/numerics/Func1.h

@@ -75,6 +75,10 @@ class Func1 : public std::enable_shared_from_this<Func1>
 
     virtual int ID() const;
 
+    virtual string type() const {
+        return "functor";
+    }
+
     //! Calls method eval to evaluate the function
     doublereal operator()(doublereal t) const;
 
@@ -296,6 +300,30 @@ class Exp1 : public Func1
 };
 
 
+//! implements the natural logarithm function (log)
+class Log1 : public Func1
+{
+public:
+    Log1(double A=1.0) {
+        m_c = A;
+    }
+
+    //! Constructor uses single parameter (factor)
+    Log1(size_t n, const vector<double>& params);
+
+    virtual string type() const {
+        return "log";
+    }
+
+    virtual double eval(double t) const {
+        return log(m_c * t);
+    }
+
+    virtual shared_ptr<Func1> derivative3() const;
+
+    virtual std::string write(const string& arg) const;
+};
+
 //! implements the power function (pow)
 class Pow1 : public Func1
 {

src/numerics/Func1.cpp

@@ -246,6 +246,32 @@ std::string Exp1::write(const std::string& arg) const
     }
 }
 
+Log1::Log1(size_t n, const vector<double>& params)
+{
+    if (params.size() != 1) {
+        throw CanteraError("Log1::Log1",
+            "Constructor needs exactly one parameter (factor).");
+    }
+    m_c = params[0];
+}
+
+shared_ptr<Func1> Log1::derivative3() const
+{
+    auto f = shared_ptr<Func1>(new Pow1(-1.));
+    if (m_c != 1.0) {
+        return newTimesConstFunction(f, m_c);
+    }
+    return f;
+}
+
+std::string Log1::write(const std::string& arg) const
+{
+    if (m_c == 1.0) {
+        return fmt::format("\\log({})", arg);
+    }
+    return fmt::format("\\log({}{})", m_c, arg);
+}
+
 /******************************************************************************/
 
 Pow1::Pow1(size_t n, const vector<double>& params)