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# recursively draw the line

I am writing a recursive program to draw the lines recursively, given the
range[min,max] and number of intervals (n) between the range.

The problem is I don't know how to draw the line in point 0.375, as you see below.
#include <iostream>
using namespace std;

void draw(double min, double max, int n);

int main()
{ draw(0,1,8);
}

void draw(double min, double max, int n)
{ if (n != 1)
{ double mid = (max - min)/2;
cout << mid << endl;
draw(min, mid, n/2);
}
}
The program output:
0.5
0.25
0.125

Here's the expected output:
0.5
0.25
0.125
0.375
0.75
0.625
0.875
Nov 13 '05 #1
5 6358
jr********@hotmail.com (Matt) writes:
I am writing a recursive program to draw the lines recursively, given the
range[min,max] and number of intervals (n) between the range.
C has no facilities for drawing lines.
The problem is I don't know how to draw the line in point 0.375, as you see below.
That's not C.
The program output:
0.5
0.25
0.125

That's not a line. Those are numbers.
--
"What is appropriate for the master is not appropriate for the novice.
You must understand the Tao before transcending structure."
--The Tao of Programming
Nov 13 '05 #2
Matt <jr********@hotmail.com> wrote:
I am writing a recursive program to draw the lines recursively, given the
range[min,max] and number of intervals (n) between the range. The problem is I don't know how to draw the line in point 0.375, as you see below.
using namespace std;
Sorry, but this a C newsgroup, there's also a C++ group in case you have
problems with C++. So let's replace this with

#include <stdio.h>
void draw(double min, double max, int n); int main()
{ draw(0,1,8);
}
You forgot to have main() return an int...
void draw(double min, double max, int n)
{ if (n != 1)
{ double mid = (max - min)/2;
You need to add the starting point of the interval here:

double mid = ( max - min ) / 2 + min;

(the mid-point between e.g. 4 and 5 is 4.5 and not just 0.5).
cout << mid << endl;
Sorry, this won't work in C, use instead

printf( "%f\n", mid );
draw(min, mid, n/2);
Now you're "drawing" the lower half of the interval but you forget to
also "draw" the upper half. You need an additional call:

draw( mid, max, n / 2 );
}
}

Regards, Jens
--
_ _____ _____
| ||_ _||_ _| Je***********@physik.fu-berlin.de
_ | | | | | |
| |_| | | | | | http://www.physik.fu-berlin.de/~toerring
\___/ens|_|homs|_|oerring
Nov 13 '05 #3
Matt wrote:
I am writing a recursive program to draw the lines recursively, given the
range[min,max] and number of intervals (n) between the range.

The problem is I don't know how to draw the line in point 0.375, as you
#include <iostream>
using namespace std;

Try comp.lang.c++

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Nov 13 '05 #4
On 5 Oct 2003 10:44:13 -0700, jr********@hotmail.com (Matt) wrote:
I am writing a recursive program to draw the lines recursively, given the
range[min,max] and number of intervals (n) between the range.

snip

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Nov 13 '05 #5
Matt wrote:

I am writing a recursive program to draw the lines recursively, given the
range[min,max] and number of intervals (n) between the range.

Search under Bresenham's Algorithm. Can also be used to draw ellipses ;-)
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Professor Emeritus of Physics
jv*@lessspamformother.virginia.edu
^^^^^^^^^^^^^^^^^^
http://galileo.phys.virginia.edu/~jvn/

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Nov 13 '05 #6

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