c++ - Use of "template<>" for static members -

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i came across code has confused me. have distilled confusion down simple case

template<typename t> struct s {     t member;     static const size_t size; };  struct u { int i; }; typedef s<u> us_t;  template<> const size_t us_t::size = sizeof(u);

q1: why need "template<>" on last line, since us_t described?

the code came across - compiles - has equivalent of this:

template<>template<> const size_t us_t::size = sizeof(u);

i'm pretty sure cut-and-paste error wasn't caught because compiled. q2: valid? if so, why? [i notice codepad.org compile code "template<>template<>".]

imagine typedef macro that's expanded @ compile time instead of pre-processor time.

then without template<> you'd have

const size_t s<u>::size = sizeof(u);

and that's not valid syntax, because you're doing template specialization


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