I need to read in a string and then an integer until the user indicates end of input (ctrl-d in linux). Again, I am stuck. Currently I have a while loop:
while (getline(cin, line))
However, that gives an entire line and then I cannot seem to separate the string from the integer. Suggestions would be most appreciated! :)
If the string and the integer is separated by whitespace;
Do this:
while(std::cin>>your_string>>your_num>>std::ws){}
You can choose your own delimiter, by writing a manipulator yourself.
Another approach would be to do it your way, and put the input line into a stringstream and extract the string and numbers from it. That approach seems roundabout to me as you get strings from a stream only to put it into another stream.
cin>>a
The above statement reads a token from standard input and stores it in the a variable. What is less known is that it also returns a bool value. When you reach the end of all standard input, the above statement would return false.
Use it in an if statement!
if(c>>a){
cout<<"End of standard input has been reached!";
}
Related
In lots of hackathon they provide testcases. So in those test cases they provide inputs in different ways through STDIN. This is one of the situation I struggle at all.
This is one kind of a input: (This is one testcase)
Mike
John
Ahmed
Sangha
Daniel
Ann
So here I have 6 inputs. But they don't provide number of inputs. So I can't use for loop or while loop to take this input. Because I don't know how many iteration I should do. So I have to take inputs until end. But this is not a input from a file. So I can't use EOF as well. This input is from STDIN. So how can I take this kind of input and store it in an array? Also I don't know how many elements should create in array. Because I don't know how many number of inputs are there. (different testcases may contain different number of inputs). How can I solve this kind of a problem?
Thank you so much for the help!
You should be able to use EOF, because stdin is a file (at least on linux)
The input here clearly shows you how many entries are presented. Note that each entry is on a newline so, considering it as a delimiter, you can parse your input stream and get the entries separated and also get the count of entries.
C++ getline() does this exactly:
istream& getline( istream& is, string& str, char delim );
Last param to getline is optional because it uses '\n' as default.
If you want to do it the raw way, you could setup a file pointer and do a lookahead for '\n' and read everything before it into new item of a variable array(vector) ...do this repeatedly until u reach EOF of stream(or filestream)
I learn to program in c++ with previous experience with python and R. Id say I understand for loops well, but now I found out that I do not know nothig about them. Here is piece of code.
for (int i = 0; i != 1; ){
string name;
getline(infile, name);
if (name == end_input){
i = 1;
}
else{
names.push_back(name);
}
}
Whole program should (and do) read names (name) from file infile and store them into names string. Than I want them to store in another file. When I look on the code, I would thing c++ do following instructions:
create integer i and set it to 0
create string name
read the line from infile and store this line into names string vector.
this will repeat unless name == end_input
From this I would say that c++ will store first line in input file again and again because I didnt tell him to jump to next line after getline the first line. But program reads all names from that file, line by line as expected by author. How is that possible?
Thank you.
getline automatically moves to the next line after reading a line.
Also a do while loop might serve your purposes better here.
When an inbuilt function does not behave as you expected, the logical next step should be to check the Documentation. If you do, you will see the following:
Extracts characters from is and stores them into str until the delimitation character delim is found (or the newline character, '\n', for (2)).
The extraction also stops if the end of file is reached in is or if some other error occurs during the input operation.
If the delimiter is found, it is extracted and discarded (i.e. it is not stored and the next input operation will begin after it).
Which answers your Question.
I would like to figure out how to read a whole line (including spaces) with std::cin. I am aware of the existence of std::getline, I would just like to figure out how to do it with std::cin so I can better understand iostream in C++. I've tried using a for loop with std::cin, however it keeps reading past the end of the line. Any help would be greatly appreciated.
Also the cin << only allows us to enter one word into a string.
However, there is a cin function that reads text containing blanks.
std::cin.get(name, MAX);
get will read all characters including spaces until Max characters have been read or the end of line character (‘\n’) is reached and will put them into the name variable.
You should decide what is MAX.
Hello again Stackoverflow, I'm here again asking a question for my C++ programming class. The problem I am facing is mostly to due with user input from the keyboard. I need to be able to take the user input to decide what function to call and what arguments to give the function. For example something like add 5 would call the add function with the argument 5. At first I tried overloading the >> operator to take both a string and an int but the problem I ran into was the program was unable to take input without the int such as deletemax so I had to throw that idea out. So now I am back to tokenizing the input but we are not allowed to use Boost for this program so I came up with something like this using sstream
bool out = false;
string token;
string In;
int num;
do
{
cout << "heap> ";
cin >> In;
istringstream iss(In);
while(getline(iss, token, ' '))
{
cout << token << endl; //I know this is incorrect but just not what to replace it with
}
out = ProcessCommand (token, num); //Takes string and int to call correct functions
} while (out != true);
The problem lies in that I'm not quite sure how to correctly tokenize the string so I can get 2 string and convert the second string to an int. Can anyone offer me some assistance? I would greatly appreciate it. Also if there is a better way to go about this than I am trying I would also like to hear it.
Thanks for any help you can give me.
Googling "C++ string tokenize" will get you plenty of hits, with the first hit being on Stackoverflow. But you should take a stab at it. I'm guessing it's the point of the exercise.
You said "argumentS", which suggests that commands you support take varying numbers of arguments. I'd break it down like this:
read a line from the user
split line into 'tokens' on space boundaries, store tokens in a list
based on the first token in the list, choose a command to execute
pass the list of tokens to the command, so it can validate/interpret them as arguments
The tricky part is #2. Do you know about container classes yet? You can use vector<string> to store the chunks you parse. To do the actual parsing, you iterate through the characters of the string. Skip whitespace until you find a non-whitespace character (or run out of characters). Save this position: start. Then skip non-whitespace until you find whitespace (or run out of characters). Save this position: end. Copy the substring represented between from start to end and copy that to your token list.
Working out the actual details of this, making sure you don't have off-by-on-errors, etc. is going to be challenging if you've never done it before, which I'm guessing is the point.
You don't need to read in the whole of user input all at once.
For example you could read in the first bit of user input (the operation, add or deletemax, etc). From there depending on the operation you could continue to read arguments from input (in the case of add) or begin performing the operation immediately (in the case of deletemax).
One way would be to have a std::map of function names as keys and required number of arguments as values. You'd read a line of input, get the function name and then decide whether you need aditional arguments. I'd write a function that'd return a vector of arguments extracted from a string stream or an empty vector in case the input was invalid.
I'm working with strings in C++. I recently came across a problem when entering strings. I'm using cin >> string; to get my string as user input. When the user enters a space into the string, the next input is automatically filled out with the remaining letters, or sometimes left blank. As the next input string is often an integer, this will result in an unpleasant bug. What's a good fix for this?
EDIT: Here's the current code:
cout << "Please print the enemy's name: ";
getline(cin, enemyName);
You probably want to get all input into the string up until the user presses enter. In that case, it can be said that what you really want is to read a "line" of text. To do that, you'd use std::getline, like so:
std::getline(cin, enemyName);
That is assuming enemyName is defined as an std::string. If enemy name is a c-style charater array, you'd want to use cin.getline, like this:
cin.getline(enemyName, sizeof(enemyName));
But, try to avoid using C-style character arrays at all in C++.
The behavior of >> with strings is intentional; it interprets whitespace characters as delimiters to stop at, so it's really best at chomping words. std::getline() (#include <string>) uses '\n' as the delimiter by default, but there's also a version of std::getline() that takes a custom delimiter character if you need it.
Use getline(cin, string); instead.
Use getline() to read in an entire line at a time.
getline (cin, string);