Converting bool to text in C

Question

Maybe this is a dumb question  but is there any way to convert a boolean value to a string such that 1 turns to  true  and 0 turns to  false    I could just use an if statement  but it would be nice to know if there is a way to do that with the language or standard libraries   Plus  I m a pedant

User · Accepted Answer

How about using the C   language itself   bool t   true  bool f   false  std  cout  lt  lt  std  noboolalpha  lt  lt  t  lt  lt          lt  lt  std  boolalpha  lt  lt  t  lt  lt  std  endl          std  cout  lt  lt  std  noboolalpha  lt  lt  f  lt  lt          lt  lt  std  boolalpha  lt  lt  f  lt  lt  std  endl    UPDATE    If you want more than 4 lines of code without any console output  please go to cppreference com s page talking about std  boolalpha and std  noboolalpha which shows you the console output and explains more about the API    Additionally using std  boolalpha will modify the global state of std  cout  you may want to restore the original behavior go here for more info on restoring the state of std  cout

User · Answer

Use boolalpha to print bool to string    std  cout  lt  lt  std  boolalpha  lt  lt  b  lt  lt  endl  std  cout  lt  lt  std  noboolalpha  lt  lt  b  lt  lt  endl    C   Reference

User · Answer

We re talking about C   right  Why on earth are we still using macros    C   inline functions give you the same speed as a macro  with the added benefit of type-safety and parameter evaluation  which avoids the issue that Rodney and dwj mentioned   inline const char   const BoolToString bool b      return b    true     false       Aside from that I have a few other gripes  particularly with the accepted answer        this is used in C  not C    if you want to use printf  instead include  lt cstdio gt     include  lt stdio h gt     instead you should use the iostream libs  include  lt iostream gt      not only is this a C include  it s totally unnecessary     include  lt stdarg h gt      Macros - not type-safe  has side-effects  Use inline functions instead    define BOOL STR b   b  true   false   inline const char   const BoolToString bool b      return b    true     false      int main  int argc  char const  argv          bool alpha   true          printf  that s C  not C         printf  BOOL STR alpha            use the iostream functionality     std  cout  lt  lt  BoolToString alpha       return 0      Cheers        DrPizza  Include a whole boost lib for the sake of a function this simple  You ve got to be kidding

User · Answer

I agree that a macro might be the best fit   I just whipped up a test case  believe me I m no good with C C   but this sounded fun     include  lt stdio h gt   include  lt stdarg h gt    define BOOL STR b   b  true   false    int main  int argc  char const  argv          bool alpha   true      printf  BOOL STR alpha         return 0

User · Answer

I use a ternary in a printf like this   printf   s n   b  true   false      If you macro it    B2S b    b   true   false     then you need to make sure whatever you pass in as  b  doesn t have any side effects   And don t forget the brackets around the  b  as you could get compile errors

User · Answer

C   has proper strings so you might as well use them   They re in the standard header string    include  lt string gt  to use them  No more strcat strcpy buffer overruns  no more missing null terminators  no more messy manual memory management  proper counted strings with proper value semantics   C   has the ability to convert bools into human-readable representations too   We saw hints at it earlier with the iostream examples  but they re a bit limited because they can only blast the text to the console  or with fstreams  a file    Fortunately  the designers of C   weren t complete idiots  we also have iostreams that are backed not by the console or a file  but by an automatically managed string buffer   They re called stringstreams    include  lt sstream gt  to get them  Then we can say   std  string bool as text bool b        std  stringstream converter      converter  lt  lt  std  boolalpha  lt  lt  b       flag boolalpha calls converter setf std  ios base  boolalpha      return converter str        Of course  we don t really want to type all that   Fortunately  C   also has a convenient third-party library named Boost that can help us out here   Boost has a nice function called lexical cast   We can use it thus   boost  lexical cast lt std  string gt  my bool    Now  it s true to say that this is higher overhead than some macro  stringstreams deal with locales which you might not care about  and create a dynamic string  with memory allocation  whereas the macro can yield a literal string  which avoids that   But on the flip side  the stringstream method can be used for a great many conversions between printable and internal representations  You can run  em backwards  boost  lexical cast lt bool gt   true   does the right thing  for example   You can use them with numbers and in fact any type with the right formatted I O operators   So they re quite versatile and useful   And if after all this your profiling and benchmarking reveals that the lexical casts are an unacceptable bottleneck  that s when you should consider doing some macro horror

User · Answer

Try this Macro   Anywhere you want the  true  or false to show up just replace it with PRINTBOOL var  where var is the bool you want the text for    define PRINTBOOL x  x  true   false

User · Answer

This post is old but now you can use std  to string to convert a lot of variable as std  string   http   en cppreference com w cpp string basic string to string

User · Answer

As long as strings can be viewed directly as a char array it s going to be really hard to convince me that std  string represents strings as first class citizens in C     Besides  combining allocation and boundedness seems to be a bad idea to me anyways

User · Answer

With C  11 you might use a lambda to get a slightly more compact code and in place usage   bool to convert true   auto bool to string      bool b  - gt  std  string       return b    true     false      std  string str  string to print - gt      std  cout lt  lt str bool to string to convert     Prints   string to print - gt  true

User · Answer

This should be fine    const char  bool cast const bool b        return b    true     false       But  if you want to do it more C  -ish     include  lt iostream gt   include  lt string gt   include  lt sstream gt  using namespace std   string bool cast const bool b        ostringstream ss      ss  lt  lt  boolalpha  lt  lt  b      return ss str       int main         cout  lt  lt  bool cast true   lt  lt    n       cout  lt  lt  bool cast false   lt  lt    n

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C  20 std  format  quot    quot  https   en cppreference com w cpp utility format formatter Standard format specification claims that the default output format will be the string by default   auto s6   std  format  quot   6  quot   true       value of s6 is  quot true   quot    and   The available bool presentation types are   none  s  Copies textual representation  true or false  or the locale-specific form  to the output  b  B  c  d  o  x  X  Uses integer presentation types with the value static cast value     Related  std  string formatting like sprintf

User · Answer

Without dragging ostream into it   constexpr char const  to c str bool b       return       std  array lt char const   2 gt   false    true    b

User · Answer

How about the simple  constexpr char const  toString bool b       return b    quot true quot     quot false quot

User · Answer

If you decide to use macros  or are using C on a future project  you should add parenthesis around the  b  in the macro expansion  I don t have enough points yet to edit other people s content     define BOOL STR b    b   true   false     This is a defensive programming technique that protects against hidden order-of-operations errors  i e   how does this evaluate for all compilers   1    2    true     false    compared to    1    2     true     false

[c++] Converting bool to text in C++

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