codesamples/C/Writeup

TITLE
C Week 2 Project
Esty (Katherine) Thomas

Goal: 

The problem in this project was to address the problem that 
a data structure full of pointers can't meaningfully be 
written to disk and then reconstructed with any guarantee
that each pointer will still refer to the same object. The 
specific type of data used was the components of polyhedrons:
faces, edges, and vertices. Each face contains a pointer to 
another face and an edge, and each edge contains pointers to two 
vertices and another edge. 

The general strategy suggested, the one that I took, was to 
create 'printable' versions of the face & edge structs (as the 
vertices have no pointers), stick them in arrays, and replace 
the pointers with array indices.


Methods: 

Pointerly edges and faces, and vertices, are implemented as in the 
provided code, except instead of a name they have an 'id', which is 
incremented with each new face, edge, or vertex (type-specific). 
Matrices are mostly implemented as in the provided code, with additions 
and modifications from my Week 1 project (but no radical changes). 
"Printable" edges and faces are implemented as suggested, with array 
indices standing in for pointers. The normal vector for a face is not 
calculated; a (0,0,0) vector stands in as default.

When a new printable edge or face is created, and when a new vertex is 
created, it is added to an array of its type at the index of its ID number.
These arrays are initialized at 50, as suggested in the assignment.
As previously implied, the pointer fields of the edge and face structs are 
replaced by the ID number of the struct pointed to, in the printable version.

The edge and face creation routines are recursive, creating new edges and faces 
as needed, checking against the master arrays. These routines do not touch the 
vertices, since those are already in their array and are presumed to not change.

The routine which prints everything to a file ('printificate") is iterative, 
printing first all the faces and then all the edges. Matrices and vertices are 
printed inside the descriptions of the face or edge to which they belong.

My test program creates four vertices describing a quadrilateral, the edges 
connecting them, and the face formed by the edges. It calls printificate on this 
2-D figure, which works as desired. It then attempts to call my reconstruct-from-file 
function ('readificate') on the output file, which completely fails, because my 
understanding of fscanf is evidently insufficient, as is my understanding of what 
is going wrong with the program. This lack of understanding means that readificate 
is a horribly tangled mess of code, in addition to not working. It is very much non-modular
and generally inferior in every way.



TRANSCRIPT:

esty-thomass-macbook:173C2 esty$ make
gcc -c -g FEV.c
gcc -o runmytest -g mytest.o matrix.o FEV.o
esty-thomass-macbook:173C2 esty$ ./runmytest

 Formatting error (matrix, face) 
 
CONTENTS OF OUTTEST:

VERTICES: 4 
EDGES: 4 
FACES: 1 
FACE:   Type: 10, ID: 0 
MATRIX: Normal Direction  Type: 13 , Dims 1, 3
0.00 0.00 0.00 
~
Next Edge: 0. 
Next Face: -1. 
~~~~
EDGE:     Type: 11, ID: 0
MATRIX: Edge Direction Type: 13 , Dims 3, 1
3.00 
0.00 
0.00 
~
VERTEX:  From Vertex   Type: 12 , ID: 0
MATRIX: Vertex Coords Type: 13 , Dims 3, 1
4.00 
0.00 
0.00 
~
~~
VERTEX:  To Vertex   Type: 12 , ID: 1
MATRIX: Vertex Coords Type: 13 , Dims 3, 1
1.00 
0.00 
0.00 
~
~~
Next Edge: 1. 
~~~
EDGE:     Type: 11, ID: 1
MATRIX: Edge Direction Type: 13 , Dims 3, 1
0.00 
-1.00 
0.00 
~
VERTEX:  From Vertex   Type: 12 , ID: 1
MATRIX: Vertex Coords Type: 13 , Dims 3, 1
1.00 
0.00 
0.00 
~
~~
VERTEX:  To Vertex   Type: 12 , ID: 2
MATRIX: Vertex Coords Type: 13 , Dims 3, 1
1.00 
1.00 
0.00 
~
~~
Next Edge: 2. 
~~~
EDGE:     Type: 11, ID: 2
MATRIX: Edge Direction Type: 13 , Dims 3, 1
1.00 
0.00 
0.00 
~
VERTEX:  From Vertex   Type: 12 , ID: 2
MATRIX: Vertex Coords Type: 13 , Dims 3, 1
1.00 
1.00 
0.00 
~
~~
VERTEX:  To Vertex   Type: 12 , ID: 3
MATRIX: Vertex Coords Type: 13 , Dims 3, 1
0.00 
1.00 
0.00 
~
~~
Next Edge: 3. 
~~~
EDGE:     Type: 11, ID: 3
MATRIX: Edge Direction Type: 13 , Dims 3, 1
-4.00 
1.00 
0.00 
~
VERTEX:  From Vertex   Type: 12 , ID: 3
MATRIX: Vertex Coords Type: 13 , Dims 3, 1
0.00 
1.00 
0.00 
~
~~
VERTEX:  To Vertex   Type: 12 , ID: 0
MATRIX: Vertex Coords Type: 13 , Dims 3, 1
4.00 
0.00 
0.00 
~
~~
Next Edge: 0. 
~~~