From: "Philip Bock" <bockfam AT icenter DOT net>
Newsgroups: comp.os.msdos.djgpp
Subject: Re: I get an error, but don't see why...
Lines: 178
X-Priority: 3
X-MSMail-Priority: Normal
X-Newsreader: Microsoft Outlook Express 5.00.2314.1300
X-MimeOLE: Produced By Microsoft MimeOLE V5.00.2314.1300
Message-ID: <wwmS3.954$1J5.73817@typhoon.mbnet.mb.ca>
Date: Fri, 29 Oct 1999 19:25:16 GMT
NNTP-Posting-Host: 207.161.236.34
X-Trace: typhoon.mbnet.mb.ca 941225116 207.161.236.34 (Fri, 29 Oct 1999 14:25:16 CDT)
NNTP-Posting-Date: Fri, 29 Oct 1999 14:25:16 CDT
Organization: MBnet Networking Inc.
To: djgpp AT delorie DOT com
DJ-Gateway: from newsgroup comp.os.msdos.djgpp
Reply-To: djgpp AT delorie DOT com

Fixed that error, and feel duly stupid. However, other more worthy errors
come to take that one's place. What I'm trying to do is create a vector
graphics renderer. So I have vector images stored as structs (called vimg),
with an array of pointers to the shapes that make up the vector drawings
(called shape). But it seems that the compiler doesn't go for the idea that
I want to designate an array in a struct without defining it's size, so I
tried just defining it as a pointer, trusting my constructor to deal with
the assignment. But when the constructor assigns the pointer a value that
points to another pointer (e.g. the beginning of the array) I get more error
messages. Not as cryptic as last time, but definitely non-helpful. How do I
fix?

Errors:
vector.cpp: In method `shape::shape(int, int, int)':
vector.cpp:139: assignment to `vector *' from `vector **'
vector.cpp: In method `vimg::vimg(int, int, int *)':
vector.cpp:147: assignment to `shape *' from `shape **'
vector.cpp:149: no match for `shape & = shape *'
vector.cpp:24: candidates are: struct shape & shape::operator =(const
shape&)

Code:
#include <allegro.h>
#include <iostream.h>
#include <conio.h>
#include <stdlib.h>

struct coord
{
 int x, y;
};

struct vector
{
 coord c1, c2;
 int color;
};

struct shape
{
 int numvects;
 int stype;
 int sfill;
 vector *vects;
 shape(int newnumvects, int newstype, int newsfill);
};

struct vimg
{
 int numvectors, numshapes;
 vector *vectors;
 shape *shapes;
 vimg(int nnumv, int nnums, int vpers[]);
};

void program_init(void);
void draw_vimg(vimg vectimg);
vimg *gen_vimg(void);
shape::shape(int newnumvects, int newstype, int newsfill);
vimg::vimg(int nnumv, int nnums);

int main(void)
{
// program_init();
// set_gfx_mode(GFX_VESA1, 640, 480, 0, 0);

 vimg *mygraphic;
 mygraphic = gen_vimg();
// draw_vimg(mygraphic);

// set_gfx_mode(GFX_TEXT, 0, 0, 0, 0);
}

void program_init(void)
{
 clrscr();
 gotoxy(37, 1);
 cout << "Atest1\n";

 cout << "Initializing Allegro library...\n";
 allegro_init();

 cout << "Setting up timer...\n";
 install_timer();

 cout << "Initializing mouse routines...";
 if (install_mouse() == -1)
  cout << "failed\n";
 else
  cout << '\n';
 cout << "Detected Operating System: ";

 if (os_type == OSTYPE_UNKNOWN)
  cout << "MS-DOS\n";
 if (os_type == OSTYPE_WIN95)
  cout << "Windows 95\n";
 if (os_type == OSTYPE_DOSEMU)
  cout << "Linux DOSEMU\n";
}

void draw_vimg(vimg vectimg, int x, int y, int xscale, int yscale)
{
 for(int a = 0; a != vectimg.numshapes; a++)
 {
  file://Code to draw one shape's outline
  for(int b = 0; b != vectimg.shapes[a].numvects; b++)
   line(screen, (vectimg.shapes[a].vects[b].c1.x*xscale)+x,
(vectimg.shapes[a].vects[b].c1.y*yscale)+y,
(vectimg.shapes[a].vects[b].c2.x*xscale)+x,
(vectimg.shapes[a].vects[b].c2.y*yscale)+y,
vectimg.shapes[a].vects[b].color);
  // Code to fill shape goes here.
 }
}

vimg *gen_vimg(void)
{
 int vpers[]={6};
 vimg newvimg(6, 1, vpers);

 newvimg.vectors[0].c1.x = 50;
 newvimg.vectors[0].c1.y = 1;
 newvimg.vectors[0].c2.x = 100;
 newvimg.vectors[0].c2.y = 1;
 newvimg.vectors[0].color = 1;
 newvimg.vectors[1].c1.x = 100;
 newvimg.vectors[1].c1.y = 1;
 newvimg.vectors[1].c2.x = 150;
 newvimg.vectors[1].c2.y = 50;
 newvimg.vectors[1].color = 1;
 newvimg.vectors[2].c1.x = 150;
 newvimg.vectors[2].c1.y = 50;
 newvimg.vectors[2].c2.x = 100;
 newvimg.vectors[2].c2.y = 100;
 newvimg.vectors[2].color = 1;
 newvimg.vectors[3].c1.x = 100;
 newvimg.vectors[3].c1.y = 100;
 newvimg.vectors[3].c2.x = 50;
 newvimg.vectors[3].c2.y = 100;
 newvimg.vectors[3].color = 1;
 newvimg.vectors[4].c1.x = 50;
 newvimg.vectors[4].c1.y = 100;
 newvimg.vectors[4].c2.x = 1;
 newvimg.vectors[4].c2.y = 50;
 newvimg.vectors[4].color = 1;
 newvimg.vectors[5].c1.x = 1;
 newvimg.vectors[5].c1.y = 50;
 newvimg.vectors[5].c2.x = 50;
 newvimg.vectors[5].c2.y = 1;
 newvimg.vectors[5].color = 1;

 newvimg.shapes[0].vects[0] = newvimg.vectors[0];
 newvimg.shapes[0].vects[1] = newvimg.vectors[1];
 newvimg.shapes[0].vects[2] = newvimg.vectors[2];
 newvimg.shapes[0].vects[3] = newvimg.vectors[3];
 newvimg.shapes[0].vects[4] = newvimg.vectors[4];
 newvimg.shapes[0].vects[5] = newvimg.vectors[5];
}

shape::shape(int newnumvects, int newstype, int newsfill)
{
 numvects = newnumvects;
 stype = newstype;
 sfill = newsfill;
 vects = new vector *[newnumvects];
}

vimg::vimg(int nnumv, int nnums, int vpers[])
{
 numvectors = nnumv;
 numshapes = nnums;
 vectors = new vector [nnumv];
 shapes = new shape *[nnums];
 for (int c = 0; c != nnums; c++)
  shapes[c] = new shape(vpers[c], 0, 0);
}