This unit implements an array and vector which can grow in size as required
during the execution of the program. The number of observations (rows) is
almost unlimmited because of the use of list and a swapfile that is created
on disk. It's written with the object Orientated Filosofie in mind and
requires Borland Pascal v7.0 (OOP-requirement) and runs in DOS Protected
Mode (Needs the DLL for the DPMI)
If anyone use this unit or makes desendents of the objects, I would greatly
appreciate if they mention my name for writing this piece of source. If you
make your own version of this objects, I would appreciate it, if you send it
to me for further development of the unit.
Contact Adress :
De Busscher Rudy
Kerselarenstraat 39
3071 Kortenberg Belgium
Details:
Before using one of the described objects you need to call the function
SwapFile_Init which returns True if the creation of a swapfile was
succesfull.
Swapfile_Done should be called at the end of the program so that
everything is cleaned up properly.
TDynArray implements an array with a fixed number of columns, maximum 100,
and an unlimited number of rows (As long as there is enough space on the
harddisk)
Var
Array : PDynArray;
Usage : Before using the array, you have to initialise it by making
an instance of the object
New(Array,Init);
And when you are finished using the array, you deinitialise it
by the statement :
Dispose(Array,Done);
The two most important methods are the Put and Get method for
accessing the array.
Array^.Put(X,Y,W);
W := Array^.Get(X,Y);
With Var W = Real; X,Y : Word;
Put places the real W in the array on the place X,Y (X = Row,
Y = Column). And Get retrieves the real at place X,Y.
Y ranges from 0 to 99, X from 0..???
If one use the get method with X and Y parameter which are greater
than the greatest one you used with put, you get a run-time error
203.
Examples
Suppose this code:
New(Array,Init);
W := Random(1);
Array^.Put(0,0,W);
Array^.Put(0,2,W);
Array^.Put(2,0,W);
Array^.Put(2,2,W);
W := Array^.Get(3,3); -> Runtime error 203
W := Array^.Get(1,1); -> Runtime Error 203
W := Array^.Get(0,1); -> Returns 0 in W
See the techincal reference for an explanation of
the last line.
When you do not need the data in the array anymore, but you don't
want to use the Destructor Done (Because you need an array in an
other part of your program and want to keep the name), you can
use the Clear method:
Array^.Clear;
It is strongly recomended using Clear or Done as soon as you
don't need the data or array anymore because of the rather strong
memory requirements of the object.
TDynFrame is a descendent of TDynArray. Besides the functionality of
TDynArray, it implements names for variables (Columns) and observation
(Rows) and opne can assign a code (Char-type) to each variable.
Usage: The methods Init, Done, Put, Get and Clear are used in the same
way as with TDynArray. The Put method is extended so that the first
time you assign a value to a row it recevies the Observation name:
Obsxxx (xxx is the row number)
Procedure Put_VarNaam(Y : Word; T : String;C : Char);
Sets the variable name of column Y to string Y to the variable
code to character C
Procedure Put_ObsNaam(X : Word; T : String);
Sets the observation name of row X to string T
Function Get_VarNaam(Y : Word) : String;
Retrieves the Variable name of column Y
Function Get_ObsNaam(X : Word) : String;
Retrieves the Observation name of row X
Function Code(Y : Word) : Char;
Retrieves the Code of variable (column) Y
TDynArray2 is another descendent of TDynArray. If you want to use more
than 100 columns, you can swap the X and Y when you call the Put and Get
method. But what if you want to allocate a matrix of 200 columns and 200
rows? TDynArray2 can allocate a fixed numer of rows (ranging from 1 to ??
, as long as there is enough memory) and unlimited number of columns.
The only difference with TDynArray is that you have the precise the number
of rows you want to use when you allocate the object.
Example
Var Array : PDynArray;
New(Array,Init(300));
Array^.Put(100,120,W); -> Ok, no error
Array^.Put(310,120,W); -> No error shall be generated, but it is
likely that another data shall be over-
written.
TDynVector implements a vector with unlimited observation. It is very
symilar to TDynArray but the Put and Get methods only accepts the X
parameter.
Technical documentation
The implementation is based on small one-dimensional arrays with 50
elements, which are combined in list for every variable / Column.
The definition is :
PObs = ^TObs;
TObs = Record
Id : Byte;
Obs : Array[0..49] Of Real;
Next : PObs;
End;
Id = Number that represent position. Id * 50 -> Starting row
Obs = One dimensional array of values
Next = Points to the a position in memory where another structure
with data is placed. (Nil of it is the last one)
When you supply an X to the Put methods, it checks of the corresponding
Id (X Div 50) exists.
If not, it creates the rows with that Id and fills them with zeros.
Suppose Var Vect : PDynVect;
Begin;
New(Vect,Init);
Vect^.Put(20,8); -> Creates vector observations 0..49 and
puts at 20 the value 8.
Vect^.Put(30,9); Puts in the same datastructure (Has also Id
0) the value 9 on position 30
Vect^.Put(101,7); -> Creates vector observations 100..149.
The range 50..99 doesn't exist and
therefore
Writeln(Vect^.Get(80)); Gives a runtime error but
Writeln(Vect^.Get(15)); Gives zero because of the initial
filling with zero.
Before it creates the datastructure TObs, it checks if there is enough
memory available. If not, it enlarges the Swapfile with 0.5 Mb.
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