Hi everyone, I started to learn cpp and encountered cin as a way to receive input from the keyboard. If I understood, cin is an object and >> is an operator defined for it. In the way it is defined, how does it "knows" to separate words from each other? and another thing, what is the meaning of: while(cin) is cin a bool type? what does it mean if it returns true or false?
+1
A:
When you use the input stream there are specific character(s) defined to separate items in the input. By default I believe it's the space character. So you can enter things separated by spaces.
Jay
2010-07-30 16:30:54
+1 because this explains how cin "knows" how to separate words from an input stream.
rturrado
2010-07-30 17:07:58
Actually, it uses any whitespace character as delimiter, which includes space, newline, tab, and more. But it's correct that it stops the current extraction when a delimiter is encountered.
Lajnold
2010-07-30 17:21:01
+3
A:
Calling:
cin >> var1 >> var2 >> var3;
is equivalent to:
cin >> var1;
cin >> var2;
cin >> var3;
As far as your other question goes, in C/C++ anything that returns a NULL or zero is treated as false in an if statement, otherwise it is treated as true.
That's why the line: if(cin) works to check whether there's more data to be read in the stream.
Jose Basilio
2010-07-30 16:32:46
Your description of `if(cin)` is not quite the whole truth. One cannot put anything as the condition; is has to be a primitive type, or otherwise "convertible" to one. In the case of std::istream, of which std::cin is an instance, this is done via `operator void*()`. While the stream is "okay", the function returns non-NULL, otherwise it returns NULL.
Lajnold
2010-07-30 17:15:22
+2
A:
"Where strm is the identifier of a istream object and variable is an object of any type supported as right parameter. It is also possible to call a succession of extraction operations as:
strm >> variable1 >> variable2 >> variable3; //...
which is the same as performing successive extractions from the same object strm" -> from operator>>
DumbCoder
2010-07-30 16:34:45