Re: [Dev-C++] How to work with *.txt files??

Per Westermark wrote:

> <>Ouch.
>
> Don't do that.
>
> There is the vector template class in the stl.

(Hielke blames himself for not reading a good C++ book himself :o)

Hm, you're right. Thanks! I said I would use a vector but in the code I 
did use an simple array. Now I think of it, the code I wrote down there 
without good thinking was ment to store an array of pointers to strings, 
not strings themselves. Used it mainly when I had to reorganize the 
order of the stored strings with manipulation members (eg. sort).
I assume that assigning pointers isn't as resourcesconsuming as 
assigning strings? However, you're still right about the complexity. 
Vector operations themselves all are lineair? So I should use a vector 
in that case too as well?

Regards,
    Hielke
    Zw...@he...

> <>Do not write a method that reallocates all strings every time.
>
> First line - allocate one string.
> Second line - allocate two strings.
> Third line - allocate three strings.
> ...
>
> By doing this, you manage to transform a linear operation - proportional
> to number of lines in the file - to become O(n^2).
>
> If you open a 100,000 line file, you would perform 100,000^2 / 2 or
> 5,000,000,000 string assigns.
>
> Never add complexity when it isn't needed.
>
> std::vector<std::string> strings;
>
> and then
>
> strings.push_back(line);
>
> or
>
> strings.reserve(10);
> strings[n++] = line;
>
> is a lot nicer code, and tremendously much more efficient.
>
> /Per W
>
> On Sat, 18 Sep 2004, hielke_prins wrote:
>
>>>>How do I refer to each line of my *.txt file???
>>>>        
>>>>
>>/*
>>   If you don't have any clue how to read a simple textfile, the first
>>thing you
>>   proably have to do is buying a good book on C(++). But here ya go.
>>
>>   I usually read small plaintext files in a vector using a simple
>>wrapperclass.
>>   Something like this (if you meant to write it in C++ at least),
>>didn't test it:
>>*/
>>
>>Class Lines
>>{
>>   string *d_line;
>>   unsigned d_nLines;
>>
>>  public:
>>   Lines(istream streamIn);
>>   /*
>>       (of course you need some simple memberfunctions
>>       returning linecount and lines on a given index too)
>>   */
>>}
>>
>>Lines::Lines(istream streamIn)
>>:
>>   d_nLines(0)
>>{
>>   string inputLine,
>>       *tempLine;
>>
>>   while(getline(streamIn, inputLine))
>>   {
>>       d_nLines++;
>>       tempLine = new string[d_nLines];
>>       for(unsigned i = 0; i < d_nLines; i++)
>>       {
>>           tempLine[i] = d_line[i];
>>       }
>>       delete d_line;
>>       d_line = tempLine;
>>   }
>>}
>>
>>Regards,
>>   Hielke
>>    
>>
>
>
>  
>