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(")");
}
