Simple lines_to_svg file not producing correct output

[canuxforryan]

The program below is a simple assignment to produce shrinking lines. I do not understand the issue that I am having. I am getting the initial line of (10, 0, 10, 400). And struct line translate is moving the x values by the desired amount (10, 20,... 390). But the struct line scale isn't working, and I don't know why. As it stands, when I compile it, it returns y values of 0. If I change the formula in struct scale to a simple addition it works. I have marked the area that is causing the problem in red. Any help would be appreciated....

To clarify, the object is to make a line move to the right by 10, and scale by 90%, with each successive line centred on the horizontal midpoint.

---

#include<stdio.h>




struct point 
    {
    float x,y;
    };


struct line 
    {
    struct point p0,p1;
    };




struct line translate(struct line line, float delta_x)
    {
    struct line line0;
        line0.p0.x = line.p0.x + delta_x;
        line0.p1.x = line.p1.x + delta_x;
                
    return line0;    


    }


struct line scale(struct line line, float factor)
    {
    struct line line0;
        line0.p0.y = line0.p0.y + (line0.p1.y * ((1 - factor)/2));
        line0.p1.y = line0.p1.y - (line0.p1.y * ((1 - factor)/2));
        
    return line0;    


    }


int main()
    {
    float origin, canvas, delta_x, factor;


    origin = 0.0;
    canvas = 400.0;
    delta_x = 10.0;
    factor = 0.90;


    printf("%.1f %.1f\n", canvas, canvas);


    struct line line;


    line.p0.x = 10.0;
    line.p0.y = origin;
    line.p1.x = 10.0;
    line.p1.y = canvas;


    printf("%f %f %f %f\n", line.p0.x, line.p0.y, line.p1.x, line.p1.y);


    struct line line0;


    line0.p0.x = line.p0.x;
    line0.p0.y = line.p0.y;
    line0.p1.x = line.p1.x;
    line0.p1.y = line.p1.y;


    while (line0.p0.x < canvas - line.p0.x)
        {    
        line0 = translate(line0, delta_x); 
        line0 = scale(line0, 0.90);


        printf("%f %f %f %f\n", 
        line0.p0.x, line0.p0.y, line0.p1.x, line0.p1.y);
        }


    return 0;
}

[tabstop]

Shouldn't you be using p0 on the first one instead of p1? EDIT: Oh, are you trying to move each the same amount. But: You're using the completely uninitialized line0, instead of the line that you passed into the function.

[canuxforryan]

The program works to move each line to the right by 10, but the scaling isn't happening.... the outputs look like this:

400.0 400.0
10.0 0.0 10.0 400.0
20.0 0.0 20.0 0.0
30.0 0.0 30.0 0.0
40.0 0.0 40.0 0.0
-
-
-
390.0 0.0 390.0 0.0

[Salem]

struct line translate(struct line line, float delta_x)
    {
    struct line line0;
        line0.p0.x = line.p0.x + delta_x;
        line0.p1.x = line.p1.x + delta_x;
                
    return line0;    


    }

Here's your question.
What is the value of line0.p0.y (and line0.p1.y) when this function returns?

Is it by any chance line.p0.y ?