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copied!<p><em><strong>1. C++ standard forbids using locally-defined classes with templates.</em></strong></p> <p><strong>14.3.1/2</strong>: <em>A local type, a type with no linkage, an unnamed type or a type compounded from any of these types shall not be used as a template-argument for a template type-parameter.</em></p> <p>A code example: </p> <pre><code> template <class T> class X { /* ... */ }; void f() { struct S { /* ... */ }; X<S> x3; // error: local type used as // template-argument X<S*> x4; // error: pointer to local type // used as template-argument } </code></pre> <p>Here is a little more reference from IBM documentation:</p> <p><em><strong>2. Declarations in a local class can only use type names, enumerations, static variables from the enclosing scope, as well as external variables and functions.</em></strong></p> <p>A Code Example: </p> <pre><code>int x; // global variable void f() // function definition { static int y; // static variable y can be used by // local class int x; // auto variable x cannot be used by // local class extern int g(); // extern function g can be used by // local class class local // local class { int g() { return x; } // error, local variable x // cannot be used by g int h() { return y; } // valid,static variable y int k() { return ::x; } // valid, global x int l() { return g(); } // valid, extern function g }; } int main() { local* z; // error: the class local is not visible return 0; } </code></pre> <p><em><strong>3. A local class cannot have static data members</em></strong></p> <p>A Code Example: </p> <pre><code>void f() { class local { int f(); // error, local class has noninline // member function int g() {return 0;} // valid, inline member function static int a; // error, static is not allowed for // local class int b; // valid, nonstatic variable }; } </code></pre>

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