C++ BinarySearchTree Inserting an element - c++

Question

So I'm getting these errors when trying to insert to a binary search tree, I've literally been stuck on this one problem for hours not knowing what to do and I couldn't find anything on the internet to help so thanks in advance.
In file included from Indexer.h:19,
from Indexer.cpp:20:
BinarySearchTree.h: In member function ‘void BinarySearchTree<Comparable>::insert(const Comparable&, BinarySearchTree<Comparable>::BinaryNode*&) [with Comparable = Word]’:
BinarySearchTree.h:108: instantiated from ‘void BinarySearchTree<Comparable>::insert(const Comparable&) [with Comparable = Word]’
Indexer.cpp:109: instantiated from here
BinarySearchTree.h:165: error: passing ‘const Word’ as ‘this’ argument of ‘bool Word::operator<(Word&)’ discards qualifiers
BinarySearchTree.h:167: error: no match for ‘operator<’ in ‘t->BinarySearchTree<Word>::BinaryNode::element < x’
Word.h:33: note: candidates are: bool Word::operator<(Word&)
make: *** [Indexer.o] Error 1
And the Code I think is creating it is from Indexer.cpp line 109
Word takes in two parameters, current being the string and count is equal to 0 for this function.
Indexer.cpp
BinarySearchTree<Word> filterTree;
Line 109: filterTree.insert(Word(current, count));
BinarySearchTree.h
void insert( const Comparable & x )
{
Line:108 insert( x, root );
}
Word.cpp :operator<
bool Word::operator<(Word &RHS)
{
if(m_wordText < RHS.GetWord())
{
return true;
}
else
return false;
}

Answer 1

Member comparators should (almost) always be const functions that take const parameters,
bool Word::operator<(Word const&) const;
Any function called within a const function must also be const itself
std::string Word::GetWord() const;
(As #NeilKirk correctly points out this should probably return std::string const&).
You should learn about const correctness as it can stop you from making silly mistakes in your code.
Also using a non-member comparator is usually preferred as it allows both sides of the expression to use conversion operators
bool operator<(Word const& lhs, Word const& rhs)
{
return lhs.GetWord() < rhs.GetWord();
}