The source can be a file, an input device, and the same can be said for the destination. It works as a medium to bring data into a program from a source or to send data from the program to a specific destination. You always want to verify that reading was successful, e.g. A stream is a sequence of data (bytes) and is used for the transportation of this data. peek() with count() in Java 9 In Java 9, for the short-circuiting operations like count(), the action in peek method will not be invoked for those elements. That said, your program doesn't check whether it could successfully read the nominator and the denominator, separated by a slash. basicistream::peek basicistream::putback basicistream::read basicistream::unget Description The template class describes an object that controls extraction of elements and encoded objects from a stream buffer with elements of type E, also known as chartype, whose character traits are determined by the class T, also known as traitstype. In this short tutorial, well focus on peek (), an often misunderstood method. peek() Returns the next character in the input stream and leaves it in the input stream as the starting point for the next read. That is, you normally compare the result of std::istream::peek() against the result of std::char_traits::to_int_type(), i.e., you'd use something like this: std::cin.peek() = std::char_traits::to_int_type('0') The Java Stream API introduces us to a powerful alternative for processing data. Read the lines into a std::string using std::getline(), then assign the string to a std::istringstream object, and extract the data from that rather than directly from istream. You probably want to skip leading whitespace before determining what the next character is, e.g., using the manipulator std::ws: (std::cin > std::ws).peek (). The result may, e.g., be std::char_traits::eof() and if the value of '0' happens to be negative (I'm not aware of any platform where it is however, e.g., the funny character from my name 'ΓΌ' is a negative value on platforms where char is signed) you wouldn't get the correct result, either. Use the peek method to check the next character: while ((istream.peek()' ') & (istream>x)) Solution 2. There are two issues with your use of std::istream::peek (): This function access the next character and does not skip leading whitespace. Instead, it is an std::char_traits::int_type (which is a fancy spelling of int). The result from std::istream::peek() is not a char.You probably want to skip leading whitespace before determining what the next character is, e.g., using the manipulator std::ws: (std::cin > std::ws).peek(). This function access the next character and does not skip leading whitespace.There are two issues with your use of std::istream::peek(): After constructing and testing the sentry object, reads the next character from the input stream without extracting it. Hence, when get() is used to get c3 we got 'r' so when we next used peek() function to get c4 we got ' o' which is the next character because the function get() already extracted the character 'p' and 'r' from the string ' program'. inttype peek() Behaves as UnformattedInputFunction. Then in the next line when we used get() then also we got p as peek() function does not extract the character from the stream. When we used peek to get a character from the string program we got 'p' i.e. The program written below can be used to understand the basic difference between peek() and get() function. In the above program we used peek() and get() functions and both of them returned the same value,
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