Use the auto keyword in C STL

Question

I have seen code which use vector   vector lt int gt s  s push back 11   s push back 22   s push back 33   s push back 55   for  vector lt int gt   iterator it   s begin    it  s end    it          cout  lt  lt   it  lt  lt  endl      It is same as  for  auto it   s begin    it    s end    it          cout  lt  lt   it  lt  lt  endl      How safe is in this case the use of the auto keyword  And what about if type of vector is float  string

User · Answer

auto keyword is intended to use in such situation  it is absolutely safe  But unfortunately it available only in C  0x so you will have portability issues with it

User · Answer

The auto keyword is simply asking the compiler to deduce the type of the variable from the initialization   Even a pre-C  0x compiler knows what the type of an  initialization  expression is  and more often than not  you can see that type in error messages    include  lt vector gt   include  lt iostream gt  using namespace std   int main         vector lt int gt s      s push back 11       s push back 22       s push back 33       s push back 55       for  int it s begin   it  s end   it             cout lt  lt  it lt  lt endl           Line 12  error  cannot convert    gnu debug   Safe iterator lt   gnu cxx    normal iterator lt int     gnu norm  vector lt int  std  allocator lt int gt   gt   gt     gnu debug def  vector lt int  std  allocator lt int gt   gt   gt   to  int  in initialization   The auto keyword simply allows you to take advantage of this knowledge - if you  compiler  know the right type  just choose for me

User · Answer

This is new item in the language which I think we are going to be struggling with for years to come  The  auto  of the start presents not only readability problem   from now on when you encounter it you will have to spend considerable time trying to figure out wtf it is just like the time that intern named all  variables xyz      but you also will spend considerable time cleaning after easily excitable programmers   like the once who replied before me  Example from above   I can bet  1000   will be written   for  auto it   s    not  for  auto amp  it   s    as a result invoking move semantics where you list expecting it  modifying your collection underneath     Another example of the problem  is your question itself  You clearly don t know much about stl iterators and you trying to overcome that gap through usage of the magic of  auto   as a result you create the code that might be problematic later on

User · Answer

The auto keyword gets the type from the expression on the right of    Therefore it will work with any type  the only requirement is to initialize the auto variable when declaring it so that the compiler can deduce the type   Examples   auto a   0 0f      a is float auto b   std  vector lt int gt         b is std  vector lt int gt     MyType foo      return MyType       auto c   foo        c is MyType

User · Answer

It s additional information  and isn t an answer   In C  11 you can write   for  auto amp  it   s        cout  lt  lt  it  lt  lt  endl      instead of   for  auto it   s begin    it    s end    it          cout  lt  lt   it  lt  lt  endl       It has the same meaning   Update  See the  Alnitak s comment also

User · Answer

If you want a code that is readable by all programmers  c    java  and others  use the original old form instead of cryptographic new features  atp  ta  DataDrawArrayInfo  ddai  for size t i   0  i  lt  m dataDraw- gt m dataDrawArrayInfoList size    i          ddai   m dataDraw- gt m dataDrawArrayInfoList i

[c++] Use the auto keyword in C++ STL

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