Microsoft Interview Question

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    how to correctly instantiate this class:

    template < template < template < class > class, class > class Param >
    struct Bogus {
    
        int foo() {
            printf("ok\n");;
        }
    };

    - 111 on October 06, 2011 in - Report Duplicate | Flag
    Microsoft C++

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of 1 vote

whoever writes this kind of code should be fired on the spot! Why is this a good interview question?

- Anonymous on October 07, 2011 | Flag Reply
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of 0 votes

I think this just shows you are not very familiar with C++ templates: believe me, I saw even more uglier constructs when dealing with STL style code..

Perhaps this concrete example is a bit "overengineered" but if you are a professional in C++, it should not pose any problem to you to solve it.

Maybe interviewer just wanted to see if what you skills really are
if you write "experienced C++ programmer" in your CV

The solution is as follows:

'Foo' is a class which takes a template parameter which is itself a template. Hence we can declare 'Param' type as follows:

template < template < class > class X, class Y >
class Param { };

main() {

    Foo< Param > tt;
    tt.foo();
}

and the code is running

- Anonymous on October 08, 2011 | Flag
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of 0 votes

check this codepad.org/FHEj9jij
it runs well

.
On uncommenting the lines in main() : codepad.org/sUM5mkBS
it gives error.

How to do it correctly?

- monish.gupta1 on October 12, 2011 | Flag
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of 0 votes

This is one way of doing this ..

template < typename X1 >
struct Foo;


template < template < int, int > class X, int A, int B>
struct Foo< X<A, B> > {
void foo() {
printf("ok, %d, %d \n", A, B);
}};

template < int X, int Y >
class Param {
int x,y;
public:
Param(){x=X; y=Y;}
void printParam(){
cout<<x<<" "<<y<<"\n";
}
};

int main() {
Param<10, 20> p;
p.printParam();

Foo< Param<10, 20> > a;
a.foo();
return 0;
}

- P on October 31, 2011 | Flag
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0
of 0 vote

@monish


template < template < int, int > class X>
struct Foo {
int foo() {
printf("ok\n");
return 0;
}};

template < int X, int Y >
class Param {
int x,y;
public:
Param(){x=X; y=Y;}
void printParam(){
cout<<x<<" "<<y<<"\n";
}
};

int main() {
Param<10, 20> p;
p.printParam();

Foo< Param> tt;
tt.foo();
return 0;
}

- MOZHI on October 13, 2011 | Flag Reply
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0
of 0 votes

the above code works out

- MOZHI on October 13, 2011 | Flag
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0
of 0 votes

Here is more discussion somewhat related to this question.

stackoverflow.com/questions/7745405/accessing-x-and-y-in-template-class-a-like-in-templatetemplateint-x-int-y-cla

- Monish on October 14, 2011 | Flag
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0
of 0 votes

nice

- siva.sai.2020 on May 14, 2012 | Flag
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0
of 0 vote

template <template <class> class X, class Y>
class Param {
};

template <template <template<class> class, class> class Param>
class Bogus {
public:
int foo() {
printf("ok\n");
}
};

int main()
{
Bogus<Param> tt;
tt.foo();
}

- Anonymous on January 01, 2012 | Flag Reply


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