Thread: simple question

scanf returns an integer, either the number of values read in, or EOF if an end of file is reached. EOF is a special termination character, specified in stdio.h, which designates the end of a file. If no values are successfully read, scanf returns 0.

taken from http://www.geocities.com/learnprogra...n4Beginner.htm

In addition, C99 states,

The scanf function returns the value of the macro EOF if an input failure occurs before any conversion. Otherwise, the scanf function returns the number of input items assigned, which can be fewer than provided for, or even zero, in the event of an early matching failure.

Originally Posted by tat

ok so if its == 1 than scanf is reading in one value and if it correctly reads in than it exits the while loop?

Code:

while ( scanf ("%d", &exp ) == 1);

is my thinking correct?

No, the loop continues while the condition is true.

While you are successfully reading text from the stdin into an integer, the loop will continue. When you fail to successfully read text from the stdin into an integer, the loop breaks.

if you want to test if a double value was successfully stored into x and an int value was stored into exp, then your thinking is correct. or so i think so... try experimenting so that u'll know for urself.

also it's like this:

Code:

 while ( scanf ("%d", &exp ) == 1);

can be translated to:

Code:

int flag=0;
flag=scanf("%d",&exp);
while(flag==1)
   flag=scanf ("%d", &exp );

From the man page:

RETURN VALUES

These functions return the number of input items assigned, which can be
fewer than provided for, or even zero, in the event of a matching fail-
ure. Zero indicates that, while there was input available, no conver-
sions were assigned; typically this is due to an invalid input character,
such as an alphabetic character for a `%d' conversion. The value EOF is
returned if an input failure occurs before any conversion such as an end-
of-file occurs. If an error or end-of-file occurs after conversion has
begun, the number of conversions which were successfully completed is
returned.

You have one conversion inf your scan set, so you check to see that one item was stored successfully.


Quzah.

correct me if im wrong but i think the number 1 indicates that there were "1" successful conversions and successful "storing" of that converted value into the variable exp.

that purpose of that test for equality is to determine if what you intended to store into those variables were indeed successfully converted and stored. else, there was a problem storing.