Question

I am trying to write some code to calculate dividend yields. I need to calculate the dividend yield (dividend/stock_price) daily. Dividends are constant. Eventually, I will have to tie the stock price to a dynamic feed, but in the meantime the stock prices may be in their own map. I inserted the dividend amounts for each stock in the class constructor because it is less computationally cumbersome than using conditional statements in the members (i.e if stock = Apple, then dividend is X). I am getting the following error message starting at the ‘[‘ before the “AAPL”:

**error C2679: binary '[' : no operator found which takes a right-hand operand of type 'const 
char [5]' (or there is no acceptable conversion) c:\boost/unordered/unordered_map.hpp(415):  
could be 'double  &boost::unordered_map<K,T>::operator [](const FinModels::Instrument *const &)'
with 
     [
          K=const FinModels::Instrument *,
          T=double
      ]
      while trying to match the argument list '(DividendMap, const char [5])'**

Can anyone help me based on my brief code below and description? Is const Symbol* incorrect type for the key?

Also, if it’s bad convention to post the fixed map values in the constructor, please let me know what is better.

Header File

public:

typedef boost::unordered_map<const Symbol*, double> Dividend_Map;
typedef Dividend_Map::iterator Dividend_MapIterator;

private:
Dividend_Map p_dividend_map;

.CPP File

p_dividend_map["AAPL"] = 0.01;
p_dividend_map["BAC"] = 0.01;
p_dividend_map["C"] = 0.01;

Answer 1

The key type for your map is a Symbol *, and you’re trying to stick a bunch of const char * into the map. This will not work unless Symbol is typedef‘d as char.

Create a Symbol object out of each symbol you want to store in the map and then add the address of that to the map.

Symbol appl("AAPL"); // assuming Symbol has a constructor taking a const char *

p_dividend_map[&appl] = 0.01;

In the example above, the lifetime of aapl must match its lifetime as a member of the map. If the lifetime of aapl expires you’ll have the map pointing to an invalid memory location.

You may want to change the map to

typedef boost::unordered_map<Symbol, double> Dividend_Map;

Then use it as

Symbol appl("AAPL");

p_dividend_map[appl] = 0.01;