C floating point to integer type conversions

Question

What are the different techniques used to convert float type of data to integer in C      include  lt iostream gt   using namespace std  struct database     int id  age    float salary      int main       struct database employee    employee id   1    employee age   23    employee salary   45678 90            How can i print this value as an integer       with out changing the salary data type in the declaration part            cout  lt  lt  endl  lt  lt  employee id  lt  lt  endl  lt  lt  employee    age  lt  lt  endl  lt  lt  employee salary  lt  lt  endl    return 0

User · Answer

the easiest technique is to just assign float to int  for example   int i  float f  f   34 0098  i   f    this will truncate everything behind floating point or you can round your float number before

User · Answer

Normal way is to   float f   3 4  int n   static cast lt int gt  f

User · Answer

For most cases  long for floats  long long for double and long double    long a  std  lround 1 5f       2l long long b  std  llround std  floor 1 5        1ll

User · Answer

I believe you can do this using a cast   float f val   3 6f  int i val    int  f val

User · Answer

Size of some float types may exceed the size of int   This example shows a safe conversion of any float type to int using the int safeFloatToInt const FloatType  amp num   function    include  lt iostream gt   include  lt limits gt  using namespace std   template  lt class FloatType gt  int safeFloatToInt const FloatType  amp num         check if float fits into integer    if   numeric limits lt int gt   digits  lt  numeric limits lt FloatType gt   digits             check if float is smaller than max int       if   num  lt  static cast lt FloatType gt   numeric limits lt int gt   max      amp  amp             num  gt  static cast lt FloatType gt   numeric limits lt int gt   min                  return static cast lt int gt  num     safe to cast         else           cerr  lt  lt   Unsafe conversion of value    lt  lt  num  lt  lt  endl            NaN is not defined for int return the largest int value         return numeric limits lt int gt   max                 else           It is safe to cast       return static cast lt int gt  num          int main       double a 2251799813685240 0     float b 43 0     double c 23333 0       unsafe cast    cout  lt  lt  safeFloatToInt a   lt  lt  endl     cout  lt  lt  safeFloatToInt b   lt  lt  endl     cout  lt  lt  safeFloatToInt c   lt  lt  endl     return 0      Result   Unsafe conversion of value 2 2518e 15 2147483647 43 23333

User · Answer

Check out the boost NumericConversion library  It will allow to explicitly control how you want to deal with issues like overflow handling and truncation

User · Answer

One thing I want to add  Sometimes  there can be precision loss  You may want to add some epsilon value first before converting  Not sure why that works    but it work    int someint    somedouble epsilon

User · Answer

What you are looking for is  type casting   typecasting  putting the type you know you want in brackets  tells the compiler you know what you are doing and are cool with it  The old way that is inherited from C is as follows   float var a   9 99  int   var b    int var a    If you had only tried to write  int var b   var a    You would have got a warning that you can t implicitly  automatically  convert a float to an int  as you lose the decimal   This is referred to as the old way as C   offers a superior alternative   static cast   this provides a much safer way of converting from one type to another  The equivalent method would be  and the way you should do it   float var x   9 99  int   var y   static cast lt int gt  var x     This method may look a bit more long winded  but it provides much better handling for situations such as accidentally requesting a  static cast  on a type that cannot be converted  For more information on the why you should be using static cast  see this question

[c++] C++ floating point to integer type conversions

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