Question

I’m getting a compiler error in reference to a method I am trying to define in the main file of a binary heap implementation. The errors all refer to the line where the method declaration for buildTable is, and the errors are as follows:

lab4.cpp:9: error: variable or field ‘buildTable’ declared void
lab4.cpp:9: error: missing template arguments before ‘table’
lab4.cpp:9: error: expected primary-expression before ‘*’ token
lab4.cpp:9: error: ‘tree’ was not declared in this scope
lab4.cpp:9: error: expected primary-expression before ‘prefix’

Here’s my code for reference:

    #include <iostream>
    #include <string>
    #include <map>
    #include <cstring>
    #include "heap.h"
    #include "huffnode.h"
    using namespace std;

    void buildTable(map table, huffnode::huffnode * tree, std::string prefix){
        if(tree->leftChild() == NULL && tree->rightChild() == NULL){
            map[tree.getLetter()] = prefix;
        else{
            buildTable(table, tree->leftChild(), prefix+"0");
            buildTable(table, tree->rightChild(), prefix+"1");
        }
    }

    int main() {

        map<char, int> code; // Constructs map <letter, frequency>
        map<char,int>::iterator it;
        map<char,string>::iterator it2;
        map<char, string> encoding;
        string input;
        getline(cin, input);
        for(int i = 0; i < input.length(); i++){        // build a map from the string
            char currLetter = input[i];
            int exist = code.count(currLetter);
            //cout << exist << endl;
            if(exist == 0){             // check if letter already has a key
                code[currLetter] = 1;
            }else{
                code[currLetter] = code[currLetter] + 1;
            }
            if(currLetter == '.'){
                break;
            }
        }
        heap binHeap;
        for (it=code.begin() ; it != code.end(); it++){             // Fill the heap
            huffnode * newHuff = new huffnode((*it).first, (*it).second);
            cout << newHuff->getLetter() << " => " << newHuff->getFreq() << endl;
            binHeap.insert(newHuff);
        }
        /*
        while(binHeap.getSize() > 0){
            cout << binHeap.extractMin()->getFreq() << endl;

        }
        */

        while(binHeap.getSize() > 1){               // build the tree
            huffnode *newLeft, *newRight;
            newLeft = binHeap.extractMin();
            newRight = binHeap.extractMin();
            huffnode * newInternal = new huffnode(newLeft, newRight);
            binHeap.insert(newInternal);
        }

        huffnode * root = binHeap.extractMin();
        buildTable(encoding, root, "");
        for (it2=encoding.begin() ; it2 != encoding.end(); it2++){              // Fill the heap
            cout <<it2->first  << " => " << it2->second << endl;
        }




    }

I tried it with and without the std:: and huffnode:: in front of the parameters, both rendered me the same error message. Thanks for any help.

Answer 1

One problem is with the parameter declaration

map table

You have not provided template parameters to the map class. Double-check this with the other places where you used map to see what is missing.