Improved display of expressions when printing them to a stream

libraries/lepton/include/lepton/Operation.h

@@ -96,6 +96,12 @@ public:
      * @param variable     the variable with respect to which the derivate should be taken
      */
     virtual ExpressionTreeNode differentiate(const std::vector<ExpressionTreeNode>& children, const std::vector<ExpressionTreeNode>& childDerivs, const std::string& variable) const = 0;
+    /**
+     * Get whether this operation should be displayed with infix notation.
+     */
+    virtual bool isInfixOperator() const {
+        return false;
+    }
     virtual bool operator!=(const Operation& op) const {
         return op.getId() != getId();
     }
@@ -264,6 +270,9 @@ public:
         return args[0]+args[1];
     }
     ExpressionTreeNode differentiate(const std::vector<ExpressionTreeNode>& children, const std::vector<ExpressionTreeNode>& childDerivs, const std::string& variable) const;
+    bool isInfixOperator() const {
+        return true;
+    }
 };
 
 class Operation::Subtract : public Operation {
@@ -286,6 +295,9 @@ public:
         return args[0]-args[1];
     }
     ExpressionTreeNode differentiate(const std::vector<ExpressionTreeNode>& children, const std::vector<ExpressionTreeNode>& childDerivs, const std::string& variable) const;
+    bool isInfixOperator() const {
+        return true;
+    }
 };
 
 class Operation::Multiply : public Operation {
@@ -308,6 +320,9 @@ public:
         return args[0]*args[1];
     }
     ExpressionTreeNode differentiate(const std::vector<ExpressionTreeNode>& children, const std::vector<ExpressionTreeNode>& childDerivs, const std::string& variable) const;
+    bool isInfixOperator() const {
+        return true;
+    }
 };
 
 class Operation::Divide : public Operation {
@@ -330,6 +345,9 @@ public:
         return args[0]/args[1];
     }
     ExpressionTreeNode differentiate(const std::vector<ExpressionTreeNode>& children, const std::vector<ExpressionTreeNode>& childDerivs, const std::string& variable) const;
+    bool isInfixOperator() const {
+        return true;
+    }
 };
 
 class Operation::Power : public Operation {
@@ -352,6 +370,9 @@ public:
         return std::pow(args[0], args[1]);
     }
     ExpressionTreeNode differentiate(const std::vector<ExpressionTreeNode>& children, const std::vector<ExpressionTreeNode>& childDerivs, const std::string& variable) const;
+    bool isInfixOperator() const {
+        return true;
+    }
 };
 
 class Operation::Negate : public Operation {

libraries/lepton/src/ParsedExpression.cpp

@@ -239,15 +239,20 @@ ExpressionProgram ParsedExpression::createProgram() const {
 }
 
 ostream& Lepton::operator<<(ostream& out, const ExpressionTreeNode& node) {
-    out << node.getOperation().getName();
-    if (node.getChildren().size() > 0) {
-        out << "(";
-        for (int i = 0; i < (int) node.getChildren().size(); i++) {
-            if (i > 0)
-                out << ", ";
-            out << node.getChildren()[i];
+    if (node.getOperation().isInfixOperator() && node.getChildren().size() == 2) {
+        out << "(" << node.getChildren()[0] << ")" << node.getOperation().getName() << "(" << node.getChildren()[1] << ")";
+    }
+    else {
+        out << node.getOperation().getName();
+        if (node.getChildren().size() > 0) {
+            out << "(";
+            for (int i = 0; i < (int) node.getChildren().size(); i++) {
+                if (i > 0)
+                    out << ", ";
+                out << node.getChildren()[i];
+            }
+            out << ")";
         }
-        out << ")";
     }
     return out;
 }