problem passing a pointer to an array of objects (strings) to a function

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January 2nd, 2003, 05:26 PM

mtcx

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problem passing a pointer to an array of objects (strings) to a function

PHP Code:


		
			
#include <iostream.h>

#include <fstream.h>

#include <stdio.h>

#include <stdlib.h>

#include <string>

#include <string.h>



basic_string<char,string_char_traits<char>,__default_alloc_template<false,0> > * wordarray(string strWords, string(* pstrWordsArray)[64]){

  string strTemp;

  string charLast = strWords.substr(strWords.length()-1,1);

  int intIndex = 0;     

  int intSpaces = 0;

  int intLoc = 0;

  

  if (charLast=="?" || charLast=="." || charLast=="!"){

      strWords.erase(strWords.length()-1);

  }

  while (intLoc != string::npos){

    intLoc = strWords.find(" ", intIndex);

    intIndex = (intLoc + 1);  

    if (intLoc != -1){

       intSpaces++;

    }  

  }

  

  intIndex = 0;

  intLoc = 0;

 

  for (int x=0; x<=intSpaces; x++){

    intLoc = strWords.find(" ", intIndex);

    (*pstrWordsArray)[x].insert(0, strWords, intIndex, intLoc);

    strTemp.insert(0, strWords, intIndex+intLoc+1, strWords.length()-intIndex+intLoc+1);

    strWords = strTemp;

    strTemp = "\0";

  }

  }

  

int main(int argc, char *argv[])

{

  

  string strWords;

  string strWordsArray[64];

  string(* pstrWordsArray)[64];

  pstrWordsArray =& strWordsArray;

  

  wordarray(pstrWordsArray, strWords); // Line 46

  

  system("PAUSE");    

  return 0;

}

The top function wordarray() should convert a group of words connected by spaces into an array with a word per index (similar to PHP's explode()). In the declaration of that function, I originally put

PHP Code:


		
			
 string wordarray(string strWords, string(* pstrWordsArray)[64])

but that gave me errors, so I used the whole basic_string thing. The variable strWords is the group of words connect by spaces. The variable strWordsArray[64] is the array that will contain the words after going through the function (64 words maximum). The variable pstrWordsArray is a pointer used to point at strWordsArray. I wanted to use a pointer so I could modify the array directly, since I could not return a string array.

The errors I received were basically:

[Warning] In function `int main(int, char **)':
Line 46: conversion from `basic_string<char,string_char_traits<char>,__default_alloc_template<false,0> > (*)[64]' to non-scalar type `basic_string<char,string_char_traits<char>,__default_alloc_template<false,0> >' requested

I would really appreciate any advice. I'm basically a newbie to C++.

January 3rd, 2003, 01:16 AM

TEMM

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im not really sure about C++ but in C you would do something like:

(this isnt totally coded im just going to half *** it in pseudo-pseudo code

)

Code:


#includes

main {
   char *sentence;
   char **words;
   
    get sentence
    getWords(sentence,words)
}

getWords(char *sentence, char**words) {
    char buffer[buffersize];
    for (i <- 0 to length of sentence)
        if (sentence[i] not seperator)
           append sentence[i] to buffer
        else
            add buffer to next array slice in words
}

hope thats what you wanted to do and helps, you can fill that in to make it work

If C++ works anything like C, you cant return a pointer from a function unless the pointer was allocated outside a function or you risk having the data destroyed by some other alloc. so you can pass in the pointer for storage.

January 3rd, 2003, 01:30 PM

mtcx

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It seems like the psedo-code you wrote uses C strings which are different than the standard C++ strings (which I am using) which are objects. Testing each character of the string was a way of doing this that I hadn't thought of. My problem really is not that I don't know how to make the inner part of the function work (I worked on it before as a seperate program and it worked fine), but that I do not know how to pass a pointer to an array of objects to a function. The pointer I am talking about was made in main(), but I need to pass it to wordarray(). I am not returning the pointer, but just using the function to modify the array directly by passing a pointer instead of passing a copy of the array. I keep getting those errors that I put in my first original post. Thank you for offering your advice.

January 3rd, 2003, 03:54 PM

TEMM

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ohhhh

I think i see whats happening

try passing the parameteres like this

wordarray(string *sentence, string **words)

January 3rd, 2003, 04:09 PM

mtcx

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I tried passing it that way and it gave me an error:

Line 55 (the line with the function call on it) no match for `*basic_string<char,string_char_traits<char>,__default_alloc_template<false,0> > &'

Why would this work anyway? Could you try to explain using the code I originally posted since I cannot use yours (doesn't use C++ strings and rewrites my already working function body). Thank you for your help.

January 4th, 2003, 08:35 PM

mtcx

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I figured out how to make it work, here's the final code.

PHP Code:


		
			
#include <iostream.h>

#include <fstream.h>

#include <stdio.h>

#include <stdlib.h>

#include <string>

#include <string.h>



basic_string<char,string_char_traits<char>,__default_alloc_template<false,0> > * wordarray(string strWords, string *pstrWordsArray){

  string strTemp;

  string charLast = strWords.substr(strWords.length()-1,1);

  int intIndex = 0;     

  int intSpaces = 0;

  int intLoc = 0;

  

  if (charLast=="?" || charLast=="." || charLast=="!"){

      strWords.erase(strWords.length()-1);

  }

  while (intLoc != string::npos){

    intLoc = strWords.find(" ", intIndex);

    intIndex = (intLoc + 1);  

    if (intLoc != -1){

       intSpaces++;

    }  

  }

  

  intIndex = 0;

  intLoc = 0;

 

  for (int x=0; x<=intSpaces; x++){

    intLoc = strWords.find(" ", intIndex);

    pstrWordsArray[x].insert(0, strWords, intIndex, intLoc);

    strTemp.insert(0, strWords, intIndex+intLoc+1, strWords.length()-intIndex+intLoc+1);

    strWords = strTemp;

    strTemp = "\0";

  }

  }

  

int main(int argc, char *argv[])

{

  

  string strWords;

  string strWordsArray[64];

  string *pstrWordsArray;

  pstrWordsArray = strWordsArray;

  

  wordarray(strWords, pstrWordsArray);

  

  system("PAUSE");    

  return 0;

}

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