请教如何做到识别其中段落与段落间的空行

ithiker 2010-10-07 12:23:44

C++如何做到识别其中段落与段落间的空行
空行判断时怎样写：if(line == " ")好像不可以
我的程序，帮忙改写下：

#include <iostream>

#include <fstream>

#include <string>

using namespace std;



int main(void)

{

	ifstream file_in;

	file_in.open("abc.txt");

	string sLine;

	int n=0;

	

	while(getline(file_in,sLine))

	{

		cout<<n++<<" ";

		if(sLine == " ")

		    cout<<"空行";

		cout<<sLine<<endl;

	}

	file_in.close();



	return 0;



}

When on board H.M.S. Beagle, as naturalist, I was much struck with certain

facts in the distribution of the organic beings inhabiting South America,

and in the geological relations of the present to the past inhabitants of

that continent.  These facts, as will be seen in the latter chapters of

this volume, seemed to throw some light on the origin of species--that

mystery of mysteries, as it has been called by one of our greatest

philosophers.  On my return home, it occurred to me, in 1837, that

something might perhaps be made out on this question by patiently

accumulating and reflecting on all sorts of facts which could possibly have

any bearing on it.  After five years' work I allowed myself to speculate on

the subject, and drew up some short notes; these I enlarged in 1844 into a

sketch of the conclusions, which then seemed to me probable:  from that

period to the present day I have steadily pursued the same object.  I hope

that I may be excused for entering on these personal details, as I give

them to show that I have not been hasty in coming to a decision.



My work is now (1859) nearly finished; but as it will take me many more

years to complete it, and as my health is far from strong, I have been

urged to publish this abstract.  I have more especially been induced to do

this, as Mr. Wallace, who is now studying the natural history of the Malay

Archipelago, has arrived at almost exactly the same general conclusions

that I have on the origin of species.  In 1858 he sent me a memoir on this

subject, with a request that I would forward it to Sir Charles Lyell, who

sent it to the Linnean Society, and it is published in the third volume of

the Journal of that Society.  Sir C. Lyell and Dr. Hooker, who both knew of

my work--the latter having read my sketch of 1844--honoured me by thinking

it advisable to publish, with Mr. Wallace's excellent memoir, some brief

extracts from my manuscripts.



This abstract, which I now publish, must necessarily be imperfect.  I

cannot here give references and authorities for my several statements; and

I must trust to the reader reposing some confidence in my accuracy.  No

doubt errors may have crept in, though I hope I have always been cautious

in trusting to good authorities alone.  I can here give only the general

conclusions at which I have arrived, with a few facts in illustration, but

which, I hope, in most cases will suffice.  No one can feel more sensible

than I do of the necessity of hereafter publishing in detail all the facts,

with references, on which my conclusions have been grounded; and I hope in

a future work to do this.  For I am well aware that scarcely a single point

is discussed in this volume on which facts cannot be adduced, often

apparently leading to conclusions directly opposite to those at which I

have arrived.  A fair result can be obtained only by fully stating and

balancing the facts and arguments on both sides of each question; and this

is here impossible.