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How are cctype header functions accessible? [duplicate]

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0

This question already has an answer here:

• 
  Why it seems not necessary to include some STL headers
  
  2 answers
  
  


• 
  Why does omission of “#include <string>” only sometimes cause compilation failures?
  
  6 answers
  
  

Character related functions are defined in the cctype header. I made a program which uses the ispunct() function defined in this header. Program is as follows:

#include <iostream>
#include <string>
#include <cctype>
using namespace std;

int main() 
 string s("Hello world!!!");
 decltype(s.size()) punct_cnt = 0;

 for(auto c : s) 
 if(ispunct(c)) 
 punct_cnt++;
 
 

 cout << "The string contains " << punct_cnt << " punctuation marks" << endl;

 return 0;

Output is trivial. However, the program works totally fine even if I omit the cctype header include directive. How is the ispunct() function still accessible?

c++ header header-files

share|improve this question

asked Mar 27 at 19:48

Navjot SinghNavjot Singh

2111111 bronze badges

marked as duplicate by NathanOliver c++
Users with the  c++ badge can single-handedly close c++ questions as duplicates and reopen them as needed.

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Mar 27 at 19:52

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  
  It works because <cctype> gets included indirectly. Don't count on such behavior. If you are going to use a function from <cctype>, include it.
  
  – R Sahu
  Mar 27 at 19:50
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Ok but from where is it included indirectly? @RSahu
  
  – Navjot Singh
  Mar 27 at 19:51
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  iostream will most likely include cctype
  
  – NathanOliver
  Mar 27 at 19:52
  
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  Ok. So using a seperate include for cctype would be considered as a best practice?
  
  – Navjot Singh
  Mar 27 at 19:54
  

  
  
  
  


• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  
  Yes. Always include what you need. It makes the code portable.
  
  – NathanOliver
  Mar 27 at 19:55
  

  
  
  
  

 | 
show 1 more comment

0

This question already has an answer here:

• 
  Why it seems not necessary to include some STL headers
  
  2 answers
  
  


• 
  Why does omission of “#include <string>” only sometimes cause compilation failures?
  
  6 answers
  
  

Character related functions are defined in the cctype header. I made a program which uses the ispunct() function defined in this header. Program is as follows:

#include <iostream>
#include <string>
#include <cctype>
using namespace std;

int main() 
 string s("Hello world!!!");
 decltype(s.size()) punct_cnt = 0;

 for(auto c : s) 
 if(ispunct(c)) 
 punct_cnt++;
 
 

 cout << "The string contains " << punct_cnt << " punctuation marks" << endl;

 return 0;

Output is trivial. However, the program works totally fine even if I omit the cctype header include directive. How is the ispunct() function still accessible?

c++ header header-files

share|improve this question

asked Mar 27 at 19:48

Navjot SinghNavjot Singh

2111111 bronze badges

marked as duplicate by NathanOliver c++
Users with the  c++ badge can single-handedly close c++ questions as duplicates and reopen them as needed.

StackExchange.ready(function()
if (StackExchange.options.isMobile) return;

$('.dupe-hammer-message-hover:not(.hover-bound)').each(function()
var $hover = $(this).addClass('hover-bound'),
$msg = $hover.siblings('.dupe-hammer-message');

$hover.hover(
function()
$hover.showInfoMessage('',
messageElement: $msg.clone().show(),
transient: false,
position: my: 'bottom left', at: 'top center', offsetTop: -7 ,
dismissable: false,
relativeToBody: true
);
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function()
StackExchange.helpers.removeMessages();

);
);
);
Mar 27 at 19:52

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  
  It works because <cctype> gets included indirectly. Don't count on such behavior. If you are going to use a function from <cctype>, include it.
  
  – R Sahu
  Mar 27 at 19:50
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Ok but from where is it included indirectly? @RSahu
  
  – Navjot Singh
  Mar 27 at 19:51
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  iostream will most likely include cctype
  
  – NathanOliver
  Mar 27 at 19:52
  
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  Ok. So using a seperate include for cctype would be considered as a best practice?
  
  – Navjot Singh
  Mar 27 at 19:54
  

  
  
  
  


• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  
  Yes. Always include what you need. It makes the code portable.
  
  – NathanOliver
  Mar 27 at 19:55
  

  
  
  
  

 | 
show 1 more comment

This question already has an answer here:

• 
  Why it seems not necessary to include some STL headers
  
  2 answers
  
  


• 
  Why does omission of “#include <string>” only sometimes cause compilation failures?
  
  6 answers
  
  

Character related functions are defined in the cctype header. I made a program which uses the ispunct() function defined in this header. Program is as follows:

#include <iostream>
#include <string>
#include <cctype>
using namespace std;

int main() 
 string s("Hello world!!!");
 decltype(s.size()) punct_cnt = 0;

 for(auto c : s) 
 if(ispunct(c)) 
 punct_cnt++;
 
 

 cout << "The string contains " << punct_cnt << " punctuation marks" << endl;

 return 0;

Output is trivial. However, the program works totally fine even if I omit the cctype header include directive. How is the ispunct() function still accessible?

c++ header header-files

share|improve this question

asked Mar 27 at 19:48

Navjot SinghNavjot Singh

2111111 bronze badges

#include <iostream>
#include <string>
#include <cctype>
using namespace std;

int main() 
 string s("Hello world!!!");
 decltype(s.size()) punct_cnt = 0;

 for(auto c : s) 
 if(ispunct(c)) 
 punct_cnt++;
 
 

 cout << "The string contains " << punct_cnt << " punctuation marks" << endl;

 return 0;

share|improve this question

asked Mar 27 at 19:48

Navjot SinghNavjot Singh

2111111 bronze badges

share|improve this question

asked Mar 27 at 19:48

Navjot SinghNavjot Singh

2111111 bronze badges

asked Mar 27 at 19:48

Navjot SinghNavjot Singh

2111111 bronze badges

asked Mar 27 at 19:48

Navjot SinghNavjot Singh

2111111 bronze badges