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(")");
}
public void apply(StackOfDouble stack, Cases cases) {
// This routine is called when an ExpressionCommand object is encountered during
// the evaluation of an ExpressionProgram. The stack may contain results of
// previous commands in the program. In this case, the command is a summation
// and the stack contains the upper and lower limits summation limits.
double upper = Math.round(stack.pop()) + 0.1; // Get summation limits.
double lower = Math.round(stack.pop());
if (Double.isNaN(upper) && Double.isNaN(lower) || upper - lower > 1000000)
stack.push(Double.NaN);
double sum = 0;
for (double x = lower; x <= upper; x++) { // Compute the sum.
sumVar.setVal(x);
sum += sumExpr.getVal();
}
stack.push(sum); // Leave the sum on the stack.
}
