Re: delimiter for istringstream

"James Kanze" <>
17 Dec 2006 13:33:39 -0500
Z.L. wrote:

I have following input string:

char* s = "1.0:2.0:3.0 4.0 5.0".

I want the ":" serve as whitespace delimiter just like blank space,
therefore when excuting

istringstream iss(s);
double digit[5];
for (int i=0; i<5; ++i) iss >> digit[i];
I can put the double type data into the array.

I remember it seems a function for istream can do this job, but I am
not so sure about that.

What exactly I mean above is whether I can specify the whitespace
delimiter for istringstream. If yes, which function does that job?

It's possible to create a ctype facet which would do this.
Creating and installing a facet is far from trivial, however,
and I would consider using facets for this sort of thing
obfuscation as well---while one expects whitespace to depend on
the locale (e.g. 0xA0 is whitespace in an ISO 8859-1 locale, but
not in an ASCII locale), one expects it to be whitespace, and
not a ':', or other punctuation.

The simplest solution is just to define a manipulator, along the
lines of std::ws, which handles this correctly, and write:

     for ( i = 0 ; i < 5 ; ++ i ) {
         if ( i != 0 ) {
             iss >> separator ;
         iss >> digit[ i ] ;

The manipulator might look something like:

     separator( std::ostream& s )
         std::ws( s ) ;
         if ( s && s.peek() == ':' ) {
             s.get() ;
             std::ws( s ) ;
         return s ;

James Kanze (Gabi Software) email:
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