Re: Use of CString key in CMap

"David Ching" <>
Fri, 04 Apr 2008 15:12:55 GMT
"Giovanni Dicanio" <> wrote in message

One of the reasons I like std::map better than CMap is that you don't need
to provide a custom hash-key generator for std::map (or, at least, I never
had to do that). Instead, it seems that you must provide that with CMap
(at least for CString key...).

I'm not sure what you mean. You don't have to provide a "custom hash-key
generator" for CMap, and I'm not sure how to do that if it is even possible.

Moreover, with std::map you can have type-safety (because you can specify
the exact template value type T), instead with CMapStringToOb the "value"
type (in "key -> value" association) is a CObject *, so you kind of loose
type safety (or at least, it is not as robust and strict as in std::map).

This is true, however, using templates you could just as well say:

  CMap<CString, CString &, CMyClass, CMyClass &> m_map;

and this has the additional advantage that CMyClass does not need to derive
from CObject.

Moreover, if you compare std::map and CMap definitions, you can note how
std::map is simpler (you just need to specify two template types: the key
type and value type - you can specify also other details, like compare
function and allocator, but default ones are also provided):

// std::map< Key, Value >
// (default compare function and allocator used)
std::map< CString, CSomeObject > m_map;

// CMap
// (You must specify 4 types...)
CMap<CString, CString &, csomecobject, csomecobject &> m_map

This is true, but siince the 2nd and 4th parameters are simply reference
types of the 1st and 3rd parameters, it's not as if it causes much brain
power to figure these out. OTOH, making sense out of STL causes significant
brain power....

-- David

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