public Node differentiate(
ASTFunNode node, String var, Node[] children, Node[] dchildren, DJep djep)
throws ParseException {
OperatorSet opset = djep.getOperatorSet();
NodeFactory nf = djep.getNodeFactory();
Operator op = opset.getMultiply();
if (mulOp != null) op = mulOp;
int nchild = node.jjtGetNumChildren();
if (nchild == 2)
return nf.buildOperatorNode(
opset.getAdd(),
nf.buildOperatorNode(op, dchildren[0], djep.deepCopy(children[1])),
nf.buildOperatorNode(op, djep.deepCopy(children[0]), dchildren[1]));
Node sums[] = new Node[nchild];
for (int i = 0; i < nchild; ++i) {
Node terms[] = new Node[nchild];
for (int j = 0; j < nchild; ++j) terms[j] = children[j];
terms[i] = dchildren[i];
sums[i] = nf.buildOperatorNode(op, terms);
}
Node res = nf.buildOperatorNode(opset.getAdd(), sums);
return res;
// throw new ParseException("Too many children "+nchild+" for "+node+"\n");
}
/**
* Differentiates a variable. May want to alter behaviour when using multi equation as diff(f,x)
* might not be zero.
*
* @return 1 if the variable has the same name as data, 0 if the variable has a different name.
*/
public Object visit(ASTVarNode node, Object data) throws ParseException {
String varName = (String) data;
XVariable var = (XVariable) node.getVar();
PartialDerivative deriv = null;
if (var instanceof DVariable) {
DVariable difvar = (DVariable) var;
if (varName.equals(var.getName())) return nf.buildConstantNode(tu.getONE());
else if (isConstantVar(var)) return nf.buildConstantNode(tu.getZERO());
deriv = difvar.findDerivative(varName, localDJep);
} else if (var instanceof PartialDerivative) {
if (isConstantVar(var)) return nf.buildConstantNode(tu.getZERO());
PartialDerivative pvar = (PartialDerivative) var;
DVariable dvar = pvar.getRoot();
deriv = dvar.findDerivative(pvar, varName, localDJep);
} else throw new ParseException("Encountered non differentiable variable");
Node eqn = deriv.getEquation();
if (eqn instanceof ASTVarNode) return nf.buildVariableNode(((ASTVarNode) eqn).getVar());
if (eqn instanceof ASTConstant) return nf.buildConstantNode(((ASTConstant) eqn).getValue());
return nf.buildVariableNode(deriv);
}
/**
* Differentiates a constant.
*
* @return 0 derivatives of constants are always zero.
*/
public Object visit(ASTConstant node, Object data) throws ParseException {
return nf.buildConstantNode(tu.getZERO());
}
