2d Arrays e FUSSY - Store data in 1d area

[gretty]

hello

I am reading a text file & trying to store some information into a 2d array.

My problem is when I go to store a piece of data into the 1st row (1d area ?:P) I get this error

error:

incompatible types in assignment of `float' to `float[25]'

For eg, I want to store 25.5 where x is
pur[x][];

My function:

float pur[53][25];   // Purchases Array [week number][purchase no.1, p2, pn...]

ifstream infile;
float x;
int count = 0; 
int count2 = 0;

while (infile >> x) {
           pur[count] = x;   // error occurs here
           
           while (x!=(char)'\n') {
                 pur[count][count2]= x;
                 count2++;
           }
           count2 = 0;
           count++;
     }

[Dave Sinkula]

float pur[53][25];
// ...
pur[count] = x; // error occurs here

If pur[count] is an array of 25 floats, and x isn't, and you get an error, isn't that enough of a hint? You seem to know how to work it here:

pur[count][count2]= x;

[kvprajapati]

Improper use of an array,

pur[count] = x; // Error

Try,

while (infile >> x) {
          if(count2==25) {
                count2=0;
                count++;
          }
      pur[count][count2]= x;
     count2++;
   }

[gretty]

Improper use of an array,

pur[count] = x; // Error

Try,

while (infile >> x) {
          if(count2==25) {
                count2=0;
                count++;
          }
      pur[count][count2]= x;
     count2++;
   }

oh, so are you saying that I cannot store 25.5 in where x is - pur[x][]? Is that not possible when I am using a 2d array?

so I cant cant go ...
cout << pur[x];
& it will output 25.5

[John A]

>Is that not possible when I am using a 2d array?
Of course not. You're using a 2D array; you need a row AND a column.

[mrnutty]

Also, from experience. I see that using 2D array to store information
from a file does not always work well. The program might not set
the file content it to proper location. I would suggest to use 1D array.

If 2D is really needed , then use 1D array, and copy it into 2D array.

[gretty]

Thanks, lol, I realise now I can do this so I have changed it. But now I have run into another problem.

I am tring to convert x, which is a float into an int. but I get this error

cannot convert `float' to `const char*' for argument `1' to `int atoi(const char*)'

Is there a way I can fix this without changing x to a 'const char' or 'char', ie, keep it as a float.

while (infile >> x) {
           count = atoi(x);   // error occurs here again
           
           while (x!=(char)'\n' || count2<=25) {
                 pur[count][count2]= x;
                 count2++;
           }
           count2 = 0;
           count++;
     }

[gretty]

Also, from experience. I see that using 2D array to store information
from a file does not always work well. The program might not set
the file content it to proper location. I would suggest to use 1D array.

If 2D is really needed , then use 1D array, and copy it into 2D array.

Thanks :), I agree, 2d arrays are tedius, I wanted to test myself by using one(2d array) in a program but I dont really HAVE to use a 2d array. I am probably going to use a vector because it will be alot more efficient (memory-wise) & alot easier

[mrnutty]

" I am tring to convert x, which is a float into an int. but I get this error"

convert float to int :

float pi = 3.14159265;
int pie1 = pi; //implicit conversion from float to int
int pie2 = int(pi); //explicit conversion from float to int, C++ style //recommended
int pie3 = (int)pi; //explicit conversion from float to int, C style

you use atoi ( a string to int ). Converts a string to int.

int i = atoi("100");

Also atoi is not a good idea. Use the standard sstream header to convert between numbers to string vice-versa.

[gretty]

thanks guys

Although I am back again with a problem, I have totally overhauled the whole function but it still uses a 2d array.

In the below code, the variable 'count' is never advanced, ie, the if statement never gets called but it should whenever we get to a line break.

float x;

while (infile >> x) {

           if  (x==(char)'\n') {    // this event never happens but it should
                cout << "count advanced\n";
                count++;          
                pCount = 0;
           }    
           else {
                pur[count][pCount]= x;
                pCount++;
           } 
     }

The file I am reading is arranged like this

Week number purchase 1 purchase 2 purchase 3 purchase n

for eg.
1 2.4 1.4
32 1.4 2.7
50 8.45 2.56

[mrnutty]

cin does read spaces or newline. For spaces and new line
you should use the .get method.

As in

ifstream inFile("a.doc");
char c;

//this will show everything in file including newline and spaces
while( inFile.get(c) ) { cout << c<<endl;}

[gretty]

Yes sorry I am back again lol :P

Thanks for the help so far but yes I have changed, AGAIN :P, how I am doing it lol. I read firstPerson's reply & I am going to use his advice, use infile.get.

But I am back at the problem of changing a string/char to a float. How can I do this?

I cant really make x a char because remember I am reading float numbers from a text file, for eg;

layout = Week number - purchase 1 - purchase 2 - purchase 3 - purchase n

for eg.
1 2.4 1.4 // taking in fractional numbers
32 1.4 2.7
50 8.45 2.56

maybe I could make x a char array of 4 elements, char x[4] ??

So my major problems are:
- how to change x to a float (from a char array or string)
- how to take in number that are more than one character long(float numbers not ints) eg 12.04 using infile.get(char x))

string x;

while (infile.get(x)) {

           if  (x=='\n') {   
                cout << "count advanced\n";
                count++;          
                pCount = 0;
           }    
           else {
                pur[count][pCount]= x;  // here I need to change x from a char to a string if x is a char array of 4 elements does [B]atof[/B] still work??
                pCount++;
           } 
     }

[mrnutty]

This is handy for you : sstream

Example :

#include<iostream>
#include<sstream>
#include<string>

using namespace std;

int main()
{
	stringstream ss;
	string myVal = "3.14159265";

	ss << myVal;

	float pi = 0;
	ss >> pi;
	cout<<"pi and pi*2 : ";
	cout<<pi <<"\t"<<pi*2<<endl;

	cout<<"\n\n";

	stringstream ss2;
	string myVal2 = "1.01 2.02 3.03";
	ss2 << myVal2;

	float val[3];
	int i = 0;
	while(ss2 >> val[i++])
		continue;

	cout<<"val contains : ";
	cout<<val[0]<<" "<<val[1]<<" "<<val[2]<<endl;
		

}