Question

So I’m making a simple geometry program, and do a test compile.

For some reason, when i compile this code, i get the following error:

base.cc: In member function ‘void seg::init_seg(p, p)’:
base.cc:20:3: error: ‘mid’ was not declared in this scope
base.cc:22:3: error: ‘b’ was not declared in this scope

But interestingly, the error doesn’t appear for points 1 and 2, only mid and b.

#include <stdio.h>
#include <stdlib.h>
#include <math.h>

struct p{
    float x=0.0f,y=0.0f;
    void init_p(float sx, float sy){
        x = sx;
        y = sy;
        }
    };

struct seg{
    p 1, 2, mid, b;
    float length = 0.0f, m = 0.0f;
    void init_seg(p p1, p p2){
        1.init_p(p1.x, p1.y);
        2.init_p(p2.x, p2.y);
        length = sqrt((1.x - 2.x)^2 + (1.y - 2.y)^2);
        mid.init_p((1.x + 2.x)/2, (1.y + 2.y)/2 );
        m = ((1.y - 2.y)/(1.x - 2.x));
        b.init_p(0, (1.y - (m*1.x)));
        }
};

Why does this error appear, and why only for these two points?

Answer 1

Here is one group of errors:

float x=0.0f,y=0.0f;
float length = 0.0f, m = 0.0f;

Unlike Java and C#, you cannot do initialization like that in C++ prior to C++11. In your case it is also unnecessary: the only constructor that you have sets both x and y, so the zeros that you are setting would be overwritten anyway.

Here is another error:

p 1, 2, mid, b;

You cannot use identifiers that do not start in a letter or an underscore. This should probably be

p p1, p2, mid, b;