! unary operator

[rakeshkool27]

hi everyone.....I am having a confusion with the implementation of condition of a while loop expression.Suppose the code

while(!feof(fp))
{
     printf("%c",ch);
     fscanf(fp,"%c",&ch);
}

Here although I have found out that that 0 means FALSE and 1 or any nonzero number means TRUE.
So if the condition is 1 the loop executes and if the loop is 0 the loop terminates.
So upto this much i could understand.
Now as we know feof returns a nonzero no. if all the characters of a file has been read else it returns 0.
So how its interpreted here by the compiler??
I mean if it is feof() is 0 then it makes it nonzero using the ! operator but what about when feof() is nonzero, whether !(nonzero number)=0?

[quzah]

Everything zero becomes "not zero", which naturally evaluates to true. Everything "not zero" becomes zero, which evaluates to false.

feof should be returning zero all the time, until it finally sees that the EOF has been reached, at which point it returns non-zero (which gets negated).


Quzah.

[vart]

for me loop

while(fscanf(fp,"%c",&ch) == 1)
{
     printf("%c",ch);
}

looks simplier

[rakeshkool27]

Everything zero becomes "not zero", which naturally evaluates to true. Everything "not zero" becomes zero, which evaluates to false.

feof should be returning zero all the time, until it finally sees that the EOF has been reached, at which point it returns non-zero (which gets negated).


Quzah.

So you mean
!(nonzero number)=0
and
!(zero)=nonzero number.......
ok thats what i wanted to know
Thanks alot

[rakeshkool27]

for me loop

while(fscanf(fp,"%c",&ch) == 1)
{
     printf("%c",ch);
}

looks simplier

whether here fscanf() returns 1 till it gets a character and returns a zero when it gets the EOF.....is it like that???I am not able to get the idea

[vart]

whether here fscanf() returns 1 till it gets a character and returns a zero when it gets the EOF.....is it like that???I am not able to get the idea

Have you read description of scanf?

the loop is basically like that:

while(you read something from file)
{
   do something with what you've read
}

fscanf returns number of tokens successfully parsed. In your case there is 1 token %c

so while fscanf returns 1 - you have something read into ch

Any other value will indicate that read failed (due to EOF condition or FAIL condition)...
In this case ch will have incorrect value and should not be processed

[rakeshkool27]

Have you read description of scanf?

the loop is basically like that:

while(you read something from file)
{
   do something with what you've read
}

fscanf returns number of tokens successfully parsed. In your case there is 1 token %c

so while fscanf returns 1 - you have something read into ch

Any other value will indicate that read failed (due to EOF condition or FAIL condition)...
In this case ch will have incorrect value and should not be processed

So incase there are more tokens as

fscanf(fp,"%c %c %c",&ch1,&ch2,&ch3);

then it should be

while(fscanf(fp,"%c %c %c",&ch1,&ch2,&ch3) == 3)

right nah????

[zacs7]

Everything zero becomes "not zero", which naturally evaluates to true. Everything "not zero" becomes zero, which evaluates to false.

Or, as per the C99 draft. The result of ! is 0 if its operand compares to unequal to 0, 1 if the value of its operand compares equal to 0. The result has type int. The expression !E is equivalent to (0 == E).

[vart]

then it should be

while(fscanf(fp,"%c %c %c",&ch1,&ch2,&ch3) == 3)

yes, like that

[rakeshkool27]

yes, like that

ok got it..........