[fpc-pascal] sorting and merging array of records

[waldo kitty]

i have a li'l project i've been wanting to do for a really long time... as i'm 
trying to do more and more with FPC, i've experimented a bit and found that i 
should be able to handle this project much easier without the old DOS 
limitations on memory usage and without having to use special stuff like 
extended and expanded memory...

so, the basics are that i'm also an amateur satellite observer... i keep up with 
the satellites via what's known as TLE (two line element) files... the ones i 
use are actually three lines where the first line is the satellite's common 
english name and the other two lines are the actual TLE element lines... there 
are certain enforced limits on these lines... as such, i have defined a record

type
   sat_name   = string[25];
   line_data  = string[69];
   two_line   = array [1..2] of line_data;
   three_line_data = record
                       satname : sat_name;
                       satdata : two_line;
                     end;

const
   max_sats = 65536;

var
   sat_data             : array [1..max_sats] of three_line_data;
   abuf                 : two_line;
   new_data             : three_line_data;

right now i'm loading the array via a simple readln into the array elements...

Procedure Input_Satellite(index : word);
   begin
   if not EOF(fsat) then
     begin
     Readln(fsat,sat_data[index].satname);
     Readln(fsat,sat_data[index].satdata[1]);
     Readln(fsat,sat_data[index].satdata[2]);
     end; {if}
   end; {Procedure Input_Satellite}

this is fine for the initial loading but i'm needing to read additional TLE 
files and insert those records into the above array... my problem is that i need 
the array sorted on a sectional value from sat_data[index].satdata[1]

   sat_catnr    := Copy(abuf[1],3,5);
and
   new_catnr    := Copy(abuf[1],3,5);

which are loaded and compared between sat_data[index].sat_data and new_data.sat_data

in the case of collisions (same catnr), i need to choose between the greater of 
a pair of values from the stored record (sat_data) and the new record (new_data) 
read from a file...

Function Real_Value(buffer : string;
               start,length : integer) : double;
   var
     result : integer;
     answer : double;
   begin
   buffer := Copy(buffer,start,length);
   Convert_Blanks(buffer);
   if buffer = '' then
     buffer := '0';
   Val(buffer,answer,result);
   if result = 0 then
     Real_Value := answer
   else
     Real_Value := 0.0;
   end; {Function Real_Value}


via...

   sat_epoch    := Real_Value(abuf[1],19,14);
and
   new_epoch    := Real_Value(abuf[1],19,14);


which are loaded and compared between sat_data[index].satdata and 
new_data.satdata...

my problem is that i cannot find any similar examples where an array of records 
is built, sorted and duplicates are eliminated based on specific factors of the 
two records being compared...

uncle has been failing me for the last several hours and i'm loosing sight of 
what i'm trying to get done... i've seen references to using a tstringlinst as 
well as something apparently non-existent called a tarray... in all of the stuff 
i've seen on tstringlinst, there's nothing that i find that is close to what i'm 
(thinking i'm) looking for... and here's where i keep getting diverted away from 
the final goal due to trying to follow everything else :/