C++ project help Generating variables.

[Nutkin]

Basicly i have to make a program that calculates the distance between x
and y points in 2d space.
the code basicly goes like this
1. User says how many points they have (max of 10)

2. User enters points

3. Using sqrt( (x2-x1)^2 + (y2-y1)^2) ) It calculates the distance
between 2 points

4. It displays the length between the first and last point.
My problem is how do i accept the data. im not sure how to vary the
number of inputs or how to declare the variables. like say the user
wants 6 points how do i let the program know only to ask the user for 6
points. and then how do i do the same calculation for each of those
points.
i tried using a while loop and heres my code so far.

#include <iostream>;
#include <cmath.h>

using namespace std;

double length(double xa,double xb,double ya,double yb)
{
double length=0;

length=sqrt(((x b-xa)*(xb-xa))+((yb-ya)*(yb-ya)));

return (length);

}

int main()

int points=0;
int ans=0;
double length(double,d ouble,double,do uble)
double xa=0;
double xb=0;
double ya=0;
double yb=0;

cout <<"How many points would you like to input (Max 10)?\n\n";
cin >>points;
while (points 1)
{
cout <<"Please enter an x value\n";
cin >>xa;
cout <<"Please enter a y value\n";
cin >>ya;
cout <<"Please enter an x value\n";
cin >>xb;
cout <<"Please enter a y value\n";
cin >>yb;

ans=ans+length( xa,xb,ya,yb)

points=points-1;
}

return (0);

Im using VC++
i know the codes a little crappy but hey thats what help is for right
:)

Thanks in advance to any genius who can sort this mess out.

[kwikius]

Jim Langston wrote:

Well, your program would work with a little modification, but what about now
you want to know the average of the distances, etc? You are not storing the
points.

Two ways, like I said. A dynamic array, or a std::vector. I believe in
your case a std::vector would be prefered.

Another alternative is a recursive function. (mag_n below). In this
case the function call stack is used to store intermediate reults:

Also makes gratuitous use of the infamous GOTO :-)

regards
Andy Little
//---------------------------------

#include <iostream>
#include <cmath>
#include <string>

// a 2D vector type
struct vect{
double x,y;
vect():x(0),y(0 ){}
vect (double const & x_in, double const & y_in)
:x(x_in),y(y_in ){}
};

inline
vect operator -(vect const & lhs, vect const & rhs)
{
return vect(lhs.x-rhs.x,lhs.y - rhs.y);
}

std::istream & operator >>(std::istre am & in, vect & pt)
{
in >pt.x >pt.y;
return in;
}

std::ostream & operator <<(std::ostre am & out, vect const & pt)
{
out <<'(' << pt.x << ','<< pt.y << ')';
return out;
}

inline
double magnitude(vect const & v)
{
return std::sqrt(v.x * v.x + v.y * v.y);
}

typedef vect point;

double mag_n( point const & p_in, int current_point, int const
num_points)
{
int next_point = current_point + 1;
std::cout << "Enter point number " << next_point << " : ";
point p;
std::cin >p;
double result = magnitude( p - p_in);
if( next_point < num_points) {
result += mag_n(p,next_po int, num_points);
}
return result;
}

int main()
{
// the infamous goto...
start:

std::cout << "Enter num points to input : ";
int num_points = 0;
std::cin >num_points; std::cout << '\n';

if ((num_points <2) || (num_points 10)){
std::cout << "Error: must be 2 <= num points <=10\n";
goto start;
}

std::cout << "Enter first point:(syntax x y) : ";
point p;
std::cin >p;
double result = mag_n(p,1, num_points) ;
std::cout << "path length = " << result <<'\n';

std::cout << "Do another set of points? (y/n) : ";
std::string str;
std::cin >str;

if ( str.substr(0,1) == "y"){
goto start;
}
}

[BobR]

kwikius wrote in message ...

>
Also makes gratuitous use of the infamous GOTO :-)
Andy Little
//---------------------------------

int main(){
start: // the infamous goto...

std::cout << "Enter num points to input : ";
int num_points = 0;
std::cin >num_points; std::cout << '\n';
if ((num_points <2) || (num_points 10)){
std::cout << "Error: must be 2 <= num points <=10\n";
goto start;
}
std::cout << "Enter first point:(syntax x y) : ";
point p;
std::cin >p;
double result = mag_n(p,1, num_points) ;
std::cout << "path length = " << result <<'\n';
std::cout << "Do another set of points? (y/n) : ";
std::string str;
std::cin >str;
if ( str.substr(0,1) == "y"){
goto start;
}
}

'goto' gives some C++ programmers 'the bends'! :-}
int main(){
// >start: // the infamous goto...

while(true){

std::cout << "Enter num points to input : ";
int num_points( 0 );
std::cin >num_points;

std::cout<< num_points << std::endl;

>
if( (num_points < 2) || (num_points 10) ){
std::cout << "Error: must be 2 <= num points <=10\n";

// goto start;
continue;

} // if(!range)

std::cout << "Enter first point:(syntax x y) : ";
point p;
std::cin >p;
double result = mag_n(p,1, num_points) ;
std::cout << "path length = " << result <<'\n';

std::cout << "Do another set of points? (y/n) : ";
std::string str;
std::cin >str;

std::cout << str <<std::endl;

>

// if ( str.substr(0,1) == "y"){ goto start; }
if ( str.substr(0,1) != "y" ){
break;
}
} // while(1)

return 0;

} // main()

--
Bob R
POVrookie

[kwikius]

BobR wrote:

'goto' gives some C++ programmers 'the bends'! :-}

I see. Sincere Apologies for that. OK, now I got rid of the gotos. How
about this version? I'm making cool use of exceptions to keep stuff
moving in this version. Better now huh?

regards
Andy Little

#include <iostream>
#include <cmath>
#include <string>
// a 2D vector type
struct vect{
double x,y;
vect():x(0),y(0 ){}
vect (double const & x_in, double const & y_in)
:x(x_in),y(y_in ){}
};
inline
vect operator -(vect const & lhs, vect const & rhs)
{
return vect(lhs.x-rhs.x,lhs.y - rhs.y);
}
std::istream & operator >>(std::istre am & in, vect & pt)
{
in >pt.x >pt.y;
return in;
}
std::ostream & operator <<(std::ostre am & out, vect const & pt)
{
out <<'(' << pt.x << ','<< pt.y << ')';
return out;
}
inline
double magnitude(vect const & v)
{
return std::sqrt(v.x * v.x + v.y * v.y);
}
typedef vect point;

double mag_n( point const & p_in, int current_point, int const
num_points)
{
int next_point = current_point + 1;
std::cout << "Enter point number " << next_point << " : ";
point p;
std::cin >p;
double result = magnitude( p - p_in);
if( next_point < num_points) {
result += mag_n(p,next_po int, num_points);
}
return result;
}

// exceptions..
struct good_input{
int n_points;
good_input(int n_points_in):n_ points(n_points _in){}
};
struct quit{ int f(){return 0;}};

int main()
{
try{
for(;;){
try{
while(1){
int num_points = 0;
std::cout << "Enter num points to input : ";
std::cin >num_points; std::cout << '\n';
if ((num_points >=2) && (num_points <= 10)){
throw good_input(num_ points);
}
else{
std::cout << "Error: must be 2 <= num points
<=10\n";
}
}
}
catch (good_input & e){

int num_points = e.n_points;
std::cout << "Enter first point:(syntax x y) : ";
point p;
std::cin >p;
double result = mag_n(p,1, num_points) ;
std::cout << "path length = " << result <<'\n';
std::cout << "Do another set of points? (y/n) : ";
std::string str;
std::cin >str;
if ( str.substr(0,1) != "y"){
throw quit();
}
}
}
}
catch (quit & e){return e.f();}
}

[BobR]

kwikius wrote in message
<11************ *********@h54g2 000cwb.googlegr oups.com>...

>BobR wrote:

>'goto' gives some C++ programmers 'the bends'! :-}

I see. Sincere Apologies for that. OK, now I got rid of the gotos. How
about this version? I'm making cool use of exceptions to keep stuff
moving in this version.

Better now huh?

<CHOKE>
First 'the bends', now 'the willies'!!

>regards
Andy Little

#include <iostream>
#include <cmath>
#include <string>

struct vect{ // a 2D vector type
double x,y;
vect():x(0),y(0 ){}
vect (double const & x_in, double const & y_in)
:x(x_in),y(y_in ){}
};

inline vect operator -(vect const & lhs, vect const & rhs){
return vect(lhs.x-rhs.x,lhs.y - rhs.y);
}

std::istream & operator >>(std::istre am & in, vect & pt){
in >pt.x >pt.y;
return in;
}

std::ostream & operator <<(std::ostre am & out, vect const & pt){
out <<'(' << pt.x << ','<< pt.y << ')';
return out;
}

inline double magnitude(vect const & v){
return std::sqrt(v.x * v.x + v.y * v.y);
}

typedef vect point;

Why a typedef? Simply rename 'vect' to 'point'. You trying to be cute? Ah,
you're 'just pulling my leg'!

>
double mag_n( point const & p_in, int current_point, int const
num_points){
int next_point = current_point + 1;
std::cout << "Enter point number " << next_point << " : ";
point p;
std::cin >p;
double result = magnitude( p - p_in);
if( next_point < num_points) {
result += mag_n(p,next_po int, num_points);
}
return result;
}

struct good_input{ // exceptions..
int n_points;
good_input(int n_points_in):n_ points(n_points _in){}
};
struct quit{ int f(){return 0;}};

int main(){
try{
for(;;){
try{
while(1){
int num_points = 0;
std::cout << "Enter num points to input : ";
std::cin >num_points; std::cout << '\n';
if ((num_points >=2) && (num_points <= 10)){
throw good_input(num_ points);
}
else{
std::cout << "Error: must be 2 <= num points
<=10\n";
}
}
}

**Gross misuse** of exceptions to control normal program flow.
It's fun to experiment, but, I wouldn't show that code to *anyone*!!

What if some newbie student saw this, and turned it in. (S)He would get an
'F'! You should have sprinkled in a few smiley faces ( :-} ) and grins (<G>)
to show you were not serious.

catch (good_input & e){
int num_points = e.n_points;
std::cout << "Enter first point:(syntax x y) : ";
point p;
std::cin >p;
double result = mag_n(p,1, num_points) ;
std::cout << "path length = " << result <<'\n';
std::cout << "Do another set of points? (y/n) : ";
std::string str;
std::cin >str;
if ( str.substr(0,1) != "y"){ throw quit(); }
}
}
}
catch (quit & e){return e.f();}
}

LMAOROF!

#include <iostream>
void Painfull(int ouch){
while(true){ for(;;){ std::cout<<" Ha Ha"; Painfull(++ouch );}}
return;
}

int main(){
Painfull(42); // <GA million laughs. [1]
}

[1] - plus or ? a gig.
--
Bob R
POVrookie

[kwikius]

BobR wrote:

kwikius wrote in message
<11************ *********@h54g2 000cwb.googlegr oups.com>...

BobR wrote:

'goto' gives some C++ programmers 'the bends'! :-}

I see. Sincere Apologies for that. OK, now I got rid of the gotos. How
about this version? I'm making cool use of exceptions to keep stuff
moving in this version.

Better now huh?

<CHOKE>
First 'the bends', now 'the willies'!!

Oh dear... sorry :-(

Why a typedef? Simply rename 'vect' to 'point'. You trying to be cute? Ah,
you're 'just pulling my leg'!

No way man!

**Gross misuse** of exceptions to control normal program flow.
It's fun to experiment, but, I wouldn't show that code to *anyone*!!

What if some newbie student saw this, and turned it in. (S)He would get an
'F'! You should have sprinkled in a few smiley faces ( :-} ) and grins (<G>)
to show you were not serious.

hmmm... back to the drawing board I guess :-(

.....;-)

regards
Andy Little

[Default User]

BobR wrote:

>
kwikius wrote in message
<11************ *********@h54g2 000cwb.googlegr oups.com>...

BobR wrote:

'goto' gives some C++ programmers 'the bends'! :-}

I see. Sincere Apologies for that. OK, now I got rid of the gotos.
How about this version? I'm making cool use of exceptions to keep
stuff moving in this version.

Better now huh?

<CHOKE>
First 'the bends', now 'the willies'!!

That's what happens when you don't have a Eustace looking out for you.

Brian

[BobR]

Default User wrote in message <4t************ *@mid.individua l.net>...

>BobR wrote:

>kwikius wrote in message
<11*********** **********@h54g 2000cwb.googleg roups.com>...

BobR wrote:
'goto' gives some C++ programmers 'the bends'! :-}

I see. Sincere Apologies for that. OK, now I got rid of the gotos.
How about this version? I'm making cool use of exceptions to keep
stuff moving in this version.

Better now huh?

<CHOKE>
First 'the bends', now 'the willies'!!

That's what happens when you don't have a Eustace looking out for you.
Brian

DANG! I just checked Fry's, and they are out of them!!

Uhhh..... what's a 'Eustace'?
[ seems I knew that once, but with my half dead single-brain-cell...]
[ ....hope it's nothing like a eunuch!! ]

--
Bob R
POVrookie

[kwikius]

Default User wrote:

BobR wrote:

kwikius wrote in message
<11************ *********@h54g2 000cwb.googlegr oups.com>...

BobR wrote:
>
>'goto' gives some C++ programmers 'the bends'! :-}
>
I see. Sincere Apologies for that. OK, now I got rid of the gotos.
How about this version? I'm making cool use of exceptions to keep
stuff moving in this version.

Better now huh?

<CHOKE>
First 'the bends', now 'the willies'!!

That's what happens when you don't have a Eustace looking out for you.

Yeah... Eustace came by and punched me on the nose and told me to stop
being a smartass!

regards
Andy Little

[Default User]

BobR wrote:

>
Default User wrote in message <4t************ *@mid.individua l.net>...

BobR wrote:

First 'the bends', now 'the willies'!!

That's what happens when you don't have a Eustace looking out for
you. Brian

DANG! I just checked Fry's, and they are out of them!!

Uhhh..... what's a 'Eustace'?
[ seems I knew that once, but with my half dead single-brain-cell...]
[ ....hope it's nothing like a eunuch!! ]

<http://en.wikipedia.or g/wiki/Next_of_Kin_(no vel)>

Brian