c++ - Implicit Template Parameters -

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the following code generates compile error in xcode:

template <typename t> struct foo {     foo(t value)     {     } };  int main() {     foo myfoo(123);     return 0; }

error: missing template arguments before 'myfoo'

changing foo myfoo(123); foo<int> myfoo(123); fixes issue, shouldn't compiler able figure out appropriate datatype?

is compiler bug, or misunderstanding implicit template parameters?

the constructor in theory infer type of object constructing, statement:

foo myfoo(123);

is allocating temporary space myfoo , must know fully-qualified type of myfoo in order know how space needed.

if want avoid typing (i.e. fingers) name of particularly complex template, consider using typedef:

typedef std::map<int, std::string> stringmap;

or in c++0x use auto keyword have compiler use type inference--though many argue leads less readable , more error-prone code, myself among them. ;p


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