public int extent(ExpressionProgram prog, int myIndex) {
// The ExpressionCommand occurs in the program prog at the index indicated by myIndex.
// Return the total number of indices in prog occupied by this command and the commands
// that generate data used by this command. In this case, that means the commands that
// compute the upper and lower limits of the summatio, plus this Cmd object.
int upper = prog.extent(myIndex - 1); // Extent of upper limit expression in prog.
int lower = prog.extent(myIndex - 1 - upper); // Extent of lower limit expression in prog.
return upper + lower + 1; // Upper + lower limits + this object.
}
public void compileDerivative(
ExpressionProgram prog, int myIndex, ExpressionProgram deriv, Variable wrt) {
// The ExpressionCommand occurs in the program prog at the index indicated by myIndex.
// Add commands to deriv that will evaluate the derivative of this command with respect to
// the variable wrt. Note that the "Cmd" object is preceded in the program by commands that
// compute the lower and upper limits of the summation.
if (!sumExpr.dependsOn(wrt)) deriv.addConstant(0);
else {
int upper = prog.extent(myIndex - 1); // Size of expression giving the upper limit.
prog.copyExpression(myIndex - 1 - upper, deriv); // Copy lower limit exression to deriv.
prog.copyExpression(myIndex - 1, deriv); // Copy upper limit expression to deriv.
deriv.addCommandObject(new Cmd(sumVar, (ExpressionProgram) sumExpr.derivative(wrt)));
}
}
public void appendOutputString(ExpressionProgram prog, int myIndex, StringBuffer buffer) {
// The ExpressionCommand occurs in the program prog at the index indicated by myIndex.
// Add a print string representation of the sub-expression represented by this command
// (including any previous commands in the program that generate data used by this
// command).
int upper = prog.extent(myIndex - 1);
buffer.append("sum(");
buffer.append(sumVar.getName());
buffer.append(", ");
prog.appendOutputString(myIndex - 1 - upper, buffer);
buffer.append(", ");
prog.appendOutputString(myIndex - 1, buffer);
buffer.append(", ");
buffer.append(sumExpr.toString());
buffer.append(")");
}
