> Hi all i am a newbie to c
> and have been reading 2ed the c language  by K&R
> i am at 1.7 functions and i am looking at the raise an int to a power and
> have two questions
> heres the prog
> #include <stdio.h>
> int power(int m,int n);
> /* test power function  */
> main()
> {
>   int i;

> for (i=0;i<10;++i)
>    printf("%d %d %d\n",i power(2,i),power(-3,i));

> /*  power raise base to n-th power; n >=0  */
> int power(int base, int n)
> {
>      int i ,p;

>     p =1;
>    for (i=1;i<=n;++i)
>        p = p * base;
> return p;
> }

> my questions are 1:
> what does i have to do in the for loop
> p isnt being increased why a  for loop??

> for (i=0;i<10;++i)
>    printf("%d %d %d\n",i power(2,i),power(-3,i));
> return 0;
> }

> /*  power raise base to n-th power; n >=0  */
> int power(int base, int n)
> {
>      int i ,p;

>     p =1;
>    for (i=1;i<=n;++i)
>        p = p * base;
> return p;
> }

> my questions are 1:
> what does i have to do in the for loop p isnt being increased why a  for
> loop??
> question2:
>  where does p come from (declared assigned ) and what has it to do with
> working out the power of some thing

> sorry if i have missed something most obvious but a iam a new learner

> > and have been reading 2ed the c language  by K&R
> > i am at 1.7 functions and i am looking at the raise an int to a power
and
> > have two questions
> > heres the prog
> > #include <stdio.h>
> > int power(int m,int n);
> > /* test power function  */
> > main()
> > {
> >   int i;

> > for (i=0;i<10;++i)
> >    printf("%d %d %d\n",i power(2,i),power(-3,i));
> > return 0;
> > }

> > /*  power raise base to n-th power; n >=0  */
> > int power(int base, int n)
> > {
> >      int i ,p;

> >     p =1;
> >    for (i=1;i<=n;++i)
> >        p = p * base;
> > return p;
> > }

> > my questions are 1:
> > what does i have to do in the for loop p isnt being increased why a  for
> > loop??
> > question2:
> >  where does p come from (declared assigned ) and what has it to do with
> > working out the power of some thing

> > sorry if i have missed something most obvious but a iam a new learner

> Both i and p are 'inventions' of the person who wrote the power function.
i
> is a counting variable, it provides a means to explicitly determine, when
> the code is written,  how many times to execute the loop.  A for loop is
the
> simplest way to do a loop when you can satisfy the a priori requirement.
i
> stands for 'index', a better choice might have been 'count'.  The writers
> chose i because this variable often *does* serve as an index.  But at this
> point in your learning process, you don't know about indexes yet, that has
> to do with arrays.

> p is acting as an accumulator.  A better name might have been
> 'current_power'.  Note that after one execution of the loop, p will be
p^1.
> And the loop is always executed at least one time.

> When I say "a better choice" above it should in no way be construed as
> criticism of the book.  It is a fantastic book!  But it is written for
> people who already have some notion of programming and the common idioms,
as
> above.   It would only be a better choice if the book were intended for
> absolute beginners.

> > Hi all i am a newbie to c
> > and have been reading 2ed the c language  by K&R
> > i am at 1.7 functions and i am looking at the raise an int to a power and
> > have two questions
> > heres the prog
> > #include <stdio.h>
> > int power(int m,int n);
> > /* test power function  */
> > main()
> > {
> >   int i;

> > for (i=0;i<10;++i)
> >    printf("%d %d %d\n",i power(2,i),power(-3,i));

> You're missing a comma.
> printf("%d %d %d\n", i, power(2, i), power(-3, i));

> > return 0;
> > }

> > /*  power raise base to n-th power; n >=0  */
> > int power(int base, int n)
> > {
> >      int i ,p;

> >     p =1;
> >    for (i=1;i<=n;++i)
> >        p = p * base;
> > return p;
> > }

> > my questions are 1:
> > what does i have to do in the for loop
> > p isnt being increased why a  for loop??

> power() could have been written without i

> int power(int base, int n)
> {
>     int p;

>     p = 1;
>     while(n--)
>        p *= base;
>     return p;
> }

>     p =1;
>    for (i=1;i<=n;++i)
>        p = p * base;
> return p;
> }

> what does i have to do in the for loop p isnt being increased

> for (i=0;i<10;++i)
>    printf("%d %d %d\n",i power(2,i),power(-3,i));

> /*  power raise base to n-th power; n >=0  */
> int power(int base, int n)
> {
>      int i ,p;

>     p =1;
>    for (i=1;i<=n;++i)
>        p = p * base;
> return p;
> }

> my questions are 1:
> what does i have to do in the for loop p isnt being increased why a  for
> loop??

> sorry if i have missed something most obvious but a iam a new learner

> thanks for takeing a moment of your time

> regards
> aade

> > > Hi all i am a newbie to c
> > > and have been reading 2ed the c language  by K&R
> > > i am at 1.7 functions and i am looking at the raise an int to a power and
> > > have two questions
> > > heres the prog
> > > #include <stdio.h>
> > > int power(int m,int n);
> > > /* test power function  */
> > > main()
> > > {
> > >   int i;

> > > for (i=0;i<10;++i)
> > >    printf("%d %d %d\n",i power(2,i),power(-3,i));

> > You're missing a comma.
> > printf("%d %d %d\n", i, power(2, i), power(-3, i));

> > > return 0;
> > > }

> > > /*  power raise base to n-th power; n >=0  */
> > > int power(int base, int n)
> > > {
> > >      int i ,p;

> > >     p =1;
> > >    for (i=1;i<=n;++i)
> > >        p = p * base;
> > > return p;
> > > }

> > > my questions are 1:
> > > what does i have to do in the for loop
> > > p isnt being increased why a  for loop??

> > power() could have been written without i

> > int power(int base, int n)
> > {
> >     int p;

> >     p = 1;
> >     while(n--)
> >        p *= base;
> >     return p;
> > }

> Change that to:

> int power(int base, int n)
> {
>     int p;

>     p = 1;
>     if (p > 0)
>         while(n--)
>             p *= base;
>     return p;
> }

> > for (i=0;i<10;++i)
> >    printf("%d %d %d\n",i power(2,i),power(-3,i));
>                          ^^
> Oops! Missed a comma ;) !

> > return 0;
> > }

> > /*  power raise base to n-th power; n >=0  */
> > int power(int base, int n)
> > {
> >      int i ,p;

> >     p =1;
> >    for (i=1;i<=n;++i)
> >        p = p * base;
> > return p;
> > }

> > my questions are 1:
> > what does i have to do in the for loop p isnt being increased why a  for
> > loop??

> Everything! You may consider i as some sort of counter that tells you
where
> you are in the process of repeated multiplication (to obtain the power).
As
> for p, it /is/ being increased in every iteration of the loop -- in fact,
it
> increases by a factor of base, every iteration.

> > question2:
> >  where does p come from (declared assigned ) and what has it to do with
> > working out the power of some thing

> The first statement in the function power() declares p, and the second
assigns
> the value 1 to it. By repeatedly multiplying p by the base (n times), you
get
> base raised to the power n (from the definition of exponentiation).

> > sorry if i have missed something most obvious but a iam a new learner

> > thanks for takeing a moment of your time

> > regards
> > aade

> I don't know if I've understood your question properly, but anyway, I hope
> this helps. Perhaps you may want to look at K&R2, Section 1.3 again.

> Cheers!

> Regards,

> M.Q.