public byte getDefaultOperandClass() 
{
        return returnClass;
}

 public short getFunctionIndex() 
{
        return field_2_fnc_index;
}

 public String getName() 
{
        return lookupName(field_2_fnc_index);
}

 public byte getParameterClass(int index) 
{
        if (index  >= paramClass.length) {
            // For var-arg (and other?) functions, the metadata does not list all the parameter
            // operand classes.  In these cases, all extra parameters are assumed to have the 
            // same operand class as the last one specified.
            return paramClass[paramClass.length - 1];
        }
        return paramClass[index];
}

 abstract public int getSize()

 public final boolean isBaseToken() 
{
        
    	return false;
}

 public boolean isExternalFunction() 
{
        return field_2_fnc_index == FUNCTION_INDEX_EXTERNAL;
}

external functions get some special processing

 public static final boolean isInternalFunctionName(String name) 
{
        short ix = FunctionMetadataRegistry.lookupIndexByName(name.toUpperCase());
        return ix  >= 0;
}

Used to detect whether a function name found in a formula is one of the standard excel functions

The name matching is case insensitive.

 protected static short lookupIndex(String name) 
{
        short ix = FunctionMetadataRegistry.lookupIndexByName(name.toUpperCase());
        if (ix <  0) {
            return FUNCTION_INDEX_EXTERNAL;
        }
        return ix;
}

Resolves internal function names into function indexes.

The name matching is case insensitive.

 protected String lookupName(short index) 
{
        if(index == FunctionMetadataRegistry.FUNCTION_INDEX_EXTERNAL) {
            return "#external#";
        }
        FunctionMetadata fm = FunctionMetadataRegistry.getFunctionByIndex(index);
        if(fm == null) {
            throw new RuntimeException("bad function index (" + index + ")");
        }
        return fm.getName();
}

 public String toFormulaString(HSSFWorkbook book) 
{
        return getName();
}

 public String toFormulaString(String[] operands) 
{
        StringBuffer buf = new StringBuffer();
        if(isExternalFunction()) {
            buf.append(operands[0]); // first operand is actually the function name
            appendArgs(buf, 1, operands);
        } else {
            buf.append(getName());
            appendArgs(buf, 0, operands);
        }
        return buf.toString();
}

 public String toString() 
{
        StringBuffer sb = new StringBuffer(64);
        sb.append(getClass().getName()).append(" [");
        sb.append(field_2_fnc_index).append(" ").append(field_1_num_args);
        sb.append("]");
        return sb.toString();
}

 abstract public  void writeBytes(byte[] array,
    int offset)