An input file is entered with the following data:
Juan Dela Cruz 150.50 5
'Juan Dela Cruz' is a name that I would like to assign to string A,
'150.50' is a number I would like to assign to float B
and 5 is a number I would like to assign to int C.
If I try cin, it is delimited by the spaces in between.
If I use getline, it's getting the whole line as a string.
What would be the correct syntax for this?
If we analyze the string, then we can make the following observation. At the very end, we have an integer. In front of the integer we have a space. And in front of that the float value. And again in fron of that a space.
So, we can simply look from the back of the string for the 2nd last space. This can easily be achieved by
size_t position = lineFromeFile.rfind(' ', lineFromeFile.rfind(' ')-1);
We need a nested statement of rfind please see here, version no 3.
Then we build a substring with the name. From start of the string up to the found position.
For the numbers, we put the rest of the original string into an std::istringstream and then simply extract from there.
Please see the following simple code, which has just a few lines of code.
#include <iostream>
#include <string>
#include <cctype>
#include <sstream>
int main() {
// This is the string that we read via getline or whatever
std::string lineFromeFile("Juan Dela Cruz 150.50 5");
// Let's search for the 2nd last space
size_t position = lineFromeFile.rfind(' ', lineFromeFile.rfind(' ')-1);
// Get the name as a substring from the original string
std::string name = lineFromeFile.substr(0, position);
// Put the numbers in a istringstream for better extraction
std::istringstream iss(lineFromeFile.substr(position));
// Get the rest of the values
float fValue;
int iValue;
iss >> fValue >> iValue;
// Show result to use
std::cout << "\nName:\t" << name << "\nFloat:\t" << fValue << "\nInt:\t" << iValue << '\n';
return 0;
}
Probably simplest in this case would be to read whole line into string and then parse it with regex:
const std::regex reg("\\s*(\\S.*)\\s+(\\d+(\\.\\d+)?)\\s+(\\d+)\\s*");
std::smatch match;
if (std::regex_match( input, match, reg)) {
auto A = match[1];
auto B = std::stof( match[2] );
auto C = std::stoi( match[4] );
} else {
// error invalid format
}
Live example
As always when the input does not (or sometimes does not) match a strict enough syntax, read the whole line and then apply the rules which to a human are "obvious".
In this case (quoting comment by john):
Read the whole string as a single line. Then analyze the string to work out where the breaks are between A, B and C. Then convert each part to the type you require.
Specifically, you probably want to use reverse searching functions (e.g. https://en.cppreference.com/w/cpp/string/byte/strrchr ), because the last parts of the input seem the most strictly formatted, i.e. easiest to parse. The rest is then the unpredictable part at the start.
either try inputting the different data type in different lines and then use line breaks to input different data types or use the distinction to differentiate different data types like adding a . or comma
use the same symbol after each data package, for example, Juan Dela Cruz;150.50;5 then you can check for a ; and separate your string there.
If you want to use the same input format you could use digits as an indicator to separate them
Related
Here's a simple code on how I read and store the data. I have a text file and inside the text file are the data that I want to pass to both number and text. The code runs fine if the text file contains text such as 2 HelloWorld1, 2 is stored into number and HelloWorld1 is stored into text.
But what if the text in the txt file is as such, 2 Hello World 1 where there are spaces between Hello, World and 1? My question is would it be possible for 2 to be stored in number and Hello World 1 to be stored in text. i understand that because of the empty spaces and as such only 2 and Hello and stored in both number and text respectively. Is there a way to overcome this?
using namespace std;
int main(){
ifstream theFile("key.txt");
int number;
string text;
while(theFile>>number>>text){
cout<<number<<" and "<<text<<endl;
}
}
You are out of luck with the default stream operator >> (if that is indeed your case).
1: Know the format
The way forward is to know the format which judging from your post you are somewhat uncertain about.
2: Use the best tools for the job
After that you choose the right tool for the job. That could involve: std::getline and handpassing, perhaps using a regex (in your case, fairly simply ones), boost::spirit, tokenization techniques, boost::string_algo, lex/bison and more.
I would add that customizing stream operator functionality (while possible) is rarely the straightforward choice.
3: Design your format to match
As an alternative to knowing the format, if you can design it, so much the better. If you have record style format, an easy way to handle strings with spaces is to put the string last - then put each record on a line. That way you may first look over each line using eg. std::getline and then just use stream operators for the rest - knowing the string will come last. Other delimiters (than linefeed) is certainly doable as well.
I would like to add an example to the very good answer of #darune.
It all depends on the input format.
Assuming that your line starts with a number and then ends with a string, you can use the following approach:
First read a number with extractor operator >>
Use getline to read the rest
Please see:
#include <iostream>
#include <string>
#include <sstream>
#include <cctype>
#include <algorithm>
#include <regex>
std::istringstream testData (
R"#(1 data1
2 data2 data3
3 data 4
)#");
int main()
{
// Definition of variables
int number{};
std::string str{};
// Read file
// Read the number
while (testData >> number)
{
// Read the rest of the line in a string
getline(testData, str);
// Remove leading and trailing spaces
str = std::regex_replace(str, std::regex("^ +| +$|( ) +"), "$1");
// Show result
std::cout << number << ' ' <<str << '\n';
};
return 0;
}
Result:
1 data1
2 data2 data3
3 data 4
But as said, it strongly depends on the input format
Good day to all,
I am having a hard time trying to extract desired integers from a string. I am given the following to read in from a file:
itemnameitemnumber price percentmarkup
examples
Gowns-u2285 24.22 37%
TwoB1Ask1-m1275 90.4 1%
What I have been trying to do is get the item number separated from the item name so that I can store the item number as a reference for sorting. As you can see the first example itemnameitemnumber is a clear cut character to digit separation, whereas the next example has numbers within its item name.
I have tried several different approaches, however with certain item names having integers apart of their name is proving to be beyond my experience.
If anyone can help me with this I would be greatly appreciative for their time and knowledge.
Good day,
I don't know, if you have a fixed number of digits for itemnumber, but i am going to assume that you don't.
This is a simple approach; first you have to separate the words of your line. For example, use std::istringstream.
When you have the line split to words, for example by giving its iterators to a vector, or reading it with operator>>, you start to check the first word from backwards, until you find anything that is not one of "0123456789 " (note the whitespace at the end).
After you've done this, you get the iterator about where these digits end (from backwards), and cut your original string, or if you have the opportunity, the already split string. Voilá! You have yourself your item name and item number.
For the record, i am going to do this whole thing, utilising the same technique for the percent markup too, of course with the exception characters being "% ".
#define VALID_DIGITS "0123456789 "
#define VALID_PERCENTAGE "% "
struct ItemData {
std::string Name;
int Count;
double Price;
double PercentMarkup;
};
int ExtractItemData(std::string Line, ItemData & Output) {
std::istringstream Stream( Line );
std::vector<std::string> Words( Stream.begin(), Stream.end() );
if (Words.size() < 3) {
/* somebody gave us a malformed line with less than needed words */
return -1;
}
// Search from backwards, until you do not find anything that is not digits (0-9) or a whitespace
std::size_t StartOfDigits = Words[0].find_last_not_of( VALID_DIGITS );
if (StartOfDigits == std::string::npos) {
/* error; your item name is invalid */
return -2;
}
else {
// Separate the string into 2 parts
Output.Name = Words[0].substr(0, StartOfDigits); // Get the first part
Output.Count = std::stoi( Words[0].substr(StartOfDigits, Words[0].length() - StartOfDigits) );
Output.Price = std::stod( Words[1] );
// Search from backwards, until we do not find anything that is not '%' or ' '
std::size_t StartOfPercent = Words[2].find_last_not_of(VALID_PERCENTAGE);
Output.PercentMarkup = std::stod( Words[2].substr(0, StartOfPercent) );
}
return 0;
}
Code requies includes sstream, vector, string, and cstdint if you do not have size_t defined
Hope the answer was useful.
Best of luck, COlda.
PS.: My first answer on stack overflow ^^;
you can iterate on the string pushing the numbers to a vector then use stringstream to convert them to integers
Here is the content of txt file that i've managed read.
X-axis=0-9
y-axis=0-9
location.txt
temp.txt
I'm not sure whether if its possible but after reading the contents of this txt file i'm trying to store just the x and y axis range into 2 variables so that i'll be able to use it for later functions. Any suggestion? And do i need to use vectors? Here is the code for reading of the file.
string configName;
ifstream inFile;
do {
cout << "Please enter config filename: ";
cin >> configName;
inFile.open(configName);
if (inFile.fail()){
cerr << "Error finding file, please re-enter again." << endl;
}
} while (inFile.fail());
string content;
string tempStr;
while (getline(inFile, content)){
if (content[0] && content[1] == '/') continue;
cout << endl << content << endl;
depends on the style of your file, if you are always sure that the style will remain unchanged, u can read the file character by character and implement pattern recognition stuff like
if (tempstr == "y-axis=")
and then convert the appropriate substring to integer using functions like
std::stoi
and store it
I'm going to assume you already have the whole contents of the .txt file in a single string somewhere. In that case, your next task should be to split the string. Personally, yes, I would recommend using vectors. Say you wanted to split that string by newlines. A function like this:
#include <string>
#include <vector>
std::vector<std::string> split(std::string str)
{
std::vector<std::string> ret;
int cur_pos = 0;
int next_delim = str.find("\n");
while (next_delim != -1) {
ret.push_back(str.substr(cur_pos, next_delim - cur_pos));
cur_pos = next_delim + 1;
next_delim = str.find("\n", cur_pos);
}
return ret;
}
Will split an input string by newlines. From there, you can begin parsing the strings in that vector. They key functions you'll want to look at are std::string's substr() and find() methods. A quick google search should get you to the relevant documentation, but here you are, just in case:
http://www.cplusplus.com/reference/string/string/substr/
http://www.cplusplus.com/reference/string/string/find/
Now, say you have the string "X-axis=0-9" in vec[0]. Then, what you can do is do a find for = and then get the substrings before and after that index. The stuff before will be "X-axis" and the stuff after will be "0-9". This will allow you to figure that the "0-9" should be ascribed to whatever "X-axis" is. From there, I think you can figure it out, but I hope this gives you a good idea as to where to start!
std::string::find() can be used to search for a character in a string;
std::string::substr() can be used to extract part of a string into another new sub-string;
std::atoi() can be used to convert a string into an integer.
So then, these three functions will allow you to do some processing on content, specifically: (1) search content for the start/stop delimiters of the first value (= and -) and the second value (- and string::npos), (2) extract them into temporary sub-strings, and then (3) convert the sub-strings to ints. Which is what you want.
I am curious as to how I would go about reading the input from a text file with no set structure (Such as notes or a small report) word by word.
The text for example might be structured like this:
"06/05/1992
Today is a good day;
The worm has turned and the battle was won."
I was thinking maybe getting the line using getline, and then seeing if I can split it into words via whitespace from there. Then I thought using strtok might work! However I don't think that will work with the punctuation.
Another method I was thinking of was getting everything char by char and omitting the characters that were undesired. Yet that one seems unlikely.
So to sort the thing short:
Is there an easy way to read an input from a file and split it into words?
Since it's easier to write than to find the duplicate question,
#include <iterator>
std::istream_iterator<std::string> word_iter( my_file_stream ), word_iter_end;
size_t wordcnt;
for ( ; word_iter != word_iter_end; ++ word_iter ) {
std::cout << "word " << wordcnt << ": " << * word_iter << '\n';
}
The std::string argument to istream_iterator tells it to return a string when you do *word_iter. Every time the iterator is incremented, it grabs another word from its stream.
If you have multiple iterators on the same stream at the same time, you can choose between data types to extract. However, in that case it may be easier just to use >> directly. The advantage of an iterator is that it can plug into the generic functions in <algorithm>.
Yes. You're looking for std::istream::operator>> :) Note that it will remove consecutive whitespace but I doubt that's a problem here.
i.e.
std::ifstream file("filename");
std::vector<std::string> words;
std::string currentWord;
while(file >> currentWord)
words.push_back(currentWord);
You can use getline with a space character, getline(buffer,1000,' ');
Or perhaps you can use this function to split a string into several parts, with a certain delimiter:
string StrPart(string s, char sep, int i) {
string out="";
int n=0, c=0;
for (c=0;c<(int)s.length();c++) {
if (s[c]==sep) {
n+=1;
} else {
if (n==i) out+=s[c];
}
}
return out;
}
Notes: This function assumes that it you have declared using namespace std;.
s is the string to be split.
sep is the delimiter
i is the part to get (0 based).
You can use the scanner technique to grabb words, numbers dates etc... very simple and flexible. The scanner normally returns token (word, number, real, keywords etc..) to a Parser.
If you later intend to interpret the words, I would recommend this approach.
I can warmly recommend the book "Writing Compilers and Interpreters" by Ronald Mak (Wiley Computer Publishing)
I need to use C++ to read in text with spaces, followed by a numeric value.
For example, data that looks like:
text1
1.0
text two
2.1
text2 again
3.1
can't be read in with 2 "infile >>" statements. I'm not having any luck with getline
either. I ultimately want to populate a struct with these 2 data elements. Any ideas?
The standard IO library isn't going to do this for you alone, you need some sort of simple parsing of the data to determine where the text ends and the numeric value begins. If you can make some simplifying assumptions (like saying there is exactly one text/number pair per line, and minimal error recovery) it wouldn't be too bad to getline() the whole thing into a string and then scan it by hand. Otherwise, you're probably better off using a regular expression or parsing library to handle this, rather than reinventing the wheel.
Why? You can use getline providing a space as line separator. Then stitch extracted parts if next is a number.
If you can be sure that your input is well-formed, you can try something like this sample:
#include <iostream>
#include <sstream>
int main()
{
std::istringstream iss("text1 1.0 text two 2.1 text2 again 3.1");
for ( ;; )
{
double x;
if ( iss >> x )
{
std::cout << x << std::endl;
}
else
{
iss.clear();
std::string junk;
if ( !(iss >> junk) )
break;
}
}
}
If you do have to validate input (instead of just trying to parse anything looking like a double from it), you'll have to write some kind of parser, which is not hard but boring.
Pseudocode.
This should work. It assumes you have text/numbers in pairs, however. You'll have to do some jimmying to get all the typing happy, also.
while( ! eof)
getline(textbuffer)
getline(numberbuffer)
stringlist = tokenize(textbuffer)
number = atof(numberbuffer)