i am creating a program to read the .dxf file of autodesk.
i am encountering a problem while reading strings.
when i use :
string acad;
fstream f;
f.open(name);
f >> acad
if the string is "chamfer" it works perfect.
but if the string is "a & b" it is able to read only upto a.
since the file format follows a pattern i am using while loop.
example from a file:
9 //loop 1
$DWGCODEPAGE //loop 1
3 //looop 1
ANSI_1252 //looop 1
9 //loop 2
$LASTSAVEDBY //loop 2
1 //loop 2
sam & tom //loop 2
9 //loop 3
$INSBASE //loop 3
10 //loop 3
0.0 //loop 3
as you can see sometimes there may not be any space as in "ANSI_1252" & sometimes there may be spaces as in "sam & tom".
how can i generalise the code so that the whole string in a line is stored along with the spaces, if any.
please forget about the spaces in the beginning of each line, i am using ws for that.
thank you!
>> operator reads words delimited by space, when used with a string parameter. If you want to read lines of characters, you should use getline() instead.
Related
I was given a question where the input will be like:
10 8
4 9
6 12
5 4
3
1
Here I don't know the number of lines that contains 2 integers. Those sets of 2 integers will be taken into an array. But when the program encounters "3", it will start taking input in another array.
I have tried this with
while(cin>>a>>b){ //some porcess with a and b }
but it doesn't work because it recognizes 3 and 1 as another set of two integers. Please help me to solve this problem.
cin >> a >> b skips not only spaces, but any delimeter characters too ('\n', '\t', ' ').
Here you actually may want to read input line-by-line and then check if there are two integers or one. Consider use of std::getline for retrieving each line of text. Then you can use read string as std::istream (like in example in the link above) and read from it with counting, how many numbers you read totally.
So think about your problem. Essentially it is, read one line at a time, and if it contains two numbers do one thing, but if it contains one number do something else.
But the code you have written reads numbers not lines. That is where the problem is.
Instead write your code to read only line at a time, analyse that line to see if it contains one or two numbers (or something else) and then proceed from there.
What you need is the ability to read a line of text into a string, and then read from that string into your numbers. To do that you use an istringstream. Something like this
#include <iostream>
#include <sstream>
#include <string>
int a, b;
string s;
getline(cin, s); // read one line from standard input
istringstream line(s); // put that string to a stream we can read from
if (line >> a) // try and read the first number from the stream
{
// got the first number
if (line >> b) // try and read the second number from the stream
{
// got the second number
...
}
else
{
// only one number
...
}
}
else
{
// didn't get any numbers, some sort of error
...
}
I have a task where I have to read different sections of an input file(.txt) of integers in c++. The file contains an unknown number of positive integers, each separated by white-space with several sentinel values of -1 placed randomly in the list to "break-up" the list into sections and another -1 at the end of the file.
Here is a sample of my input file(.txt):
3 54 35 4 9 16 -1 14 57 32 4 6 8 41 2 -1 5 6 54 21 3 -1
Here is what I've attempted so far:
int data[20],
index = 0;
ifstream fin;
fin.open("data_file.txt");
while (index < 20 && data[index] != -1 && fin >> data[index])
{
cout << data[index] << endl;
index++;
}
I can't get this to read past the first SV even if I repeat this while loop. It always just starts at the beginning of the file.
How do I read again STARTING AFTER the first SV to the second SV? The only methods I know involve reading a file from beginning to end. How do I read seperate sections?
Thanks in advance for any help,
Cheers
It sounds like you just want to group information from the file. I will not provide code since you didn't, but I may help you with the logic:
Create a file object, 2d vector, and a string
Read from the file object to the string
if the value is equal to "-1", then add a new row. Else, add a new column
The result will be a 2d vector with the rows being each group, and the columns being each positive number in that group.
I'm trying to read this file and store each row in one array. Can someone please tell me how to implement the code for this?
2
2 10 1 2 7
3 8 3 7 7 10 7
I have the code below and I can save every element of the text file into an array, but I need to have the lines saved into seperate arrays. How do I do this?
fstream myfile("myfile's_address", ios_base::in);
int a;
while (myfile >> a)
{
word[increment] = a;
increment++;
}
First, use ifstream instead of fstream with ios_base::in.
Next, use std::getline() to get one line as a string, create one vector for it (perhaps in a vector<vector<string>>), then parse it (perhaps using std::istringstream).
I am trying to figure out how to read two matrices from one file and then assign them to two different 2D arrays. The matrices are separated by a new line in the text file. I managed to get the first one to read successfully but now I cant figure out how to read the second one. The way I see it, the the line that separates the two matrices must be considered and checked for. How do I get the program to read and assign the second matrix to an array?
Both matrices and arrays are 4x4.
This is what the text file looks like:
3 4 5 7
5 16 7 12
11 12 3 9
9 8 1 12
15 4 3 6
1 12 3 12
7 8 19 9
11 12 8 5
Here is my code for the first array which works fine.
for (int y = 0; y < 4; ++y )
{
for (int x = 0; x < 4; ++x )
{
infile >> array1[x][y];
}
}
And here is my code for the array I can't figure out.
for (int y = 0; y < 4; ++y )
{
for (int x = 0; x < 4; ++x )
{
if(x == '\n' && y == '\n') //My attempt.
{
infile >> array2[x][y];
}
}
}
Here is the output:
This will check to make sure numbers in file are written to the first array.
3 4 5 7
5 16 7 12
11 12 3 9
9 8 1 12
This will check to make sure numbers in file are written to the second array.
9.21742e-314 1.0572e-307 7.29112e-304 3.87184e-306
1.06498e-307 1.65425e-317 6.79039e-313 4.22748e+266
5.92879e-323 1.06196e-307 6.95089e-308 9.88799e-315
1.79648e-313 8.48798e-314 6.95224e-308 1.06193e-307
Press any key to continue . . .
Any help is appreciated!
When you are reading your file using the "formatted input" operator >>, the kind and amount whitespace (spaces, tabs, newlines) between the items (numbers in your case) is insignificant. This means you do not get to see the empty line at all. If you need to parse a file based on its lines, consider using getline instead and parsing the single lines using a istringstream.
If on the other hand you know the size of both arrays, you can simply read the second array just as you read the first array. The extra empty line just gets ignored.
The reason your code for reading the second array does not work is that you compare the index variables to '\n', which happens to be 10 on most systems. As your index ranges from 0 to 3, the if condition is never true, so nothing gets read at all, so you are seeing a dump of uninitialized memory.
You can read the second array exactly as you read the first. The reason is that, when you start reading from a stream, at first it discards whitespaces till it encounters something that is not whitespace. Then it gets the numbers/character one by one till it encounters whitespace again. So, there is no problem with the newline and you can read the remaining array without problems.
In a file which has an xml like format (but is not xml)
<mgrwt event="1">
<rscale> 1 1234</rscale>
<asrwt>0 4234</asrwt>
<pdfrwt beam="1"> 1 2 0.11790045E+00 0.22210436E+03</pdfrwt>
<pdfrwt beam="2"> 1 -2 0.92962177E-02 0.22210436E+03</pdfrwt>
<totfact> 0.34727485E+01</totfact>
<matchscale> 0.10000000E+11 0.41999999E+02 0.61496031E+02</matchscale>
</mgrwt>
I would like with C++ to read in the file (this I know ;-) block-by block , and then assign variables to sub-components of each block, - I know for example that all numbers in
<pdfrwt beam="1"> 1 2 0.11790045E+00 0.22210436E+03</pdfrwt>
ie 1 2 0.11790045E+00 0.22210436E+03 are always numbers, and never string,so question is , how can I strip/read from each line in each block the separated-by-space numbers ?
I also tried this Read input numbers separated by spaces but could not help me..
thanks
I suggest reading line by line and using std::istringstream to parse the string.
For example, you could find out where the start of the number is by searching for the first >.
Either advance the stringstream by this amount or ...
Create a substring contain all the text before the '<'.
Create an istringstream using this substring.
Then try something like:
unsigned int first, second;
double third, fourth;
string_stream >> first >> second >> third >> fourth;