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When I try to compile the code
istream in;
if (argc==1)
in=cin;
else
{
ifstream ifn(argv[1]);
in=ifn;
}
gcc fails, complaining that operator= is private. Is there any way to set an istream to different values based on a condition?
567
The cin object in C++ is an object of class iostream. It is used to accept the input from the standard input device i.e. keyboard. It is associated with the standard C input stream stdin. The extraction operator(>>) is used along with the object cin for reading inputs.
cin is a predefined variable that reads data from the keyboard with the extraction operator ( >> ).
This can be considered as inefficient method of reading user input, why? Because when we read the user input string using cin then only the first word of the string is stored in char array and rest get ignored. The cin function considers the space in the string as delimiter and ignore the part after it.
The cin object is used to accept input from the standard input device i.e. keyboard. It is defined in the iostream header file.
You could use a pointer for in, e.g.:
istream *in;
ifstream ifn;
if (argc==1) {
in=&cin;
} else {
ifn.open(argv[1]);
in=&ifn;
}
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