How to recognise whitespaces in c++ by using '>>' operator. I kknow that'>>' will neglect spaces.

I am trying to read from a file which contains some code. My goal is to separate tokens and display them. I am writing code in c++.





For Example,





If input is:


void main()


{


int n;


}





Output should be





Keyword void


keyword main


separator (


separator )


separator {


keyword int


identifier n


separator ;


separator }








Now my problem is that


i am trying to read from the file using %26gt;%26gt; operator


i.e


char s;


ifstream infile;


infile%26gt;%26gt;s





This fragment of code reads the data from the file character by character. The %26gt;%26gt; operator in c++ will not consider whitespaces. So as soon as it completes reading 'void' it is neglecting whitespace and start reading 'main'. So it is taking 'voidmain' as a single string and giving output as





identifier voidmain





What should i do to check for whitespace between the 'void' and 'main'


so that i can get the correct out put





keyword void


keyword main





Can u please help me out





Regards,


Prudeesh C Makkapati,


Graduate Teaching Assistant,


Computer Science Dept.


University of Alabama in Huntsville

How to recognise whitespaces in c++ by using '%26gt;%26gt;' operator. I kknow that'%26gt;%26gt;' will neglect spaces.
You're probably reading in one character at a time.


Use strings (STL).





#include %26lt;string%26gt;





string s;


ifstream f;





"f %26gt;%26gt; s;" will read in one word at a time.
Reply:You could either use the functions


get() // returns the next character


get(c) // puts next character in c


getline(s, n, t) // gets n number of characters up until t, use t=' ' (space), puts result into string s. t is not included in s


get(s, n, t) // like getline except leaves t on the stream





Or, use the manipulator 'noskipws' do not skip whitespace.


infile %26gt;%26gt; noskipws; // after this is will skip whitespace


so you could use the line


infile %26gt;%26gt; s; // afterwards.





If you need to change it back, use


infile %26gt;%26gt; skipws;