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Pascal and Delphi Discussion Thread
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Aug 17th, 2009

why i cant write records into file in turbo-pascal???

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hi,

whenever i try to write records into the file, only the first piece of records can be written. even some simple program like the following cant work properly.

(Toggle Plain Text)

type thing=record
           name:string;
           end;      
var f:file of thing;
    data:array [1..2] of thing;
    i:integer;
begin
     assign(f, 'infile.txt');
     rewrite(f);
     data[1].name:='name';
     data[2].name:='second';
     for i:= 1 to 2 do
     write(f, data[i]);
     
     close(f);


end.

when i open 'infile.txt', only 'name' is shown but not 'name ' and 'second'. however, turbo-pascal works perfectly when array is written back into text file.

(Toggle Plain Text)

var f:text;
    data:array [ 1..2 ] of string;
    i:integer;
begin
     assign(f, 'infile.txt');
     rewrite(f);
     data[1]:='name';
     data[2]:='second';
     for i:=1 to 2 do
         writeln(f, data[i]);
     close(f);
end.

in this program, both 'name' and 'second' are shown. i am using both turbo-pascal and dev-pascal. is it the problem of my problem or the pascal software?????
thx for help!!!

grace

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amazing_grace

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Aug 17th, 2009

Re: why i cant write records into file in turbo-pascal???

your first program working properly!I run your code and it is worked perfectly....(of course mine is Turbo Pascal 7.0 and dev pascal 1.9.2)
listen your code:

pascal Syntax (Toggle Plain Text)
for i:= 1 to 2 do write(f, data[i]);
for i:= 1 to 2 do write(f, data[i]);

there are two rounds so this code write two records to this file

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Aug 18th, 2009

Re: why i cant write records into file in turbo-pascal???

maybe i should try the program in another computer XSS

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Aug 19th, 2009

Re: why i cant write records into file in turbo-pascal???

I'm programming under windows xp

Last edited by FlamingClaw; Aug 19th, 2009 at 4:26 am.

FlamingClaw

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Aug 23rd, 2009

Re: why i cant write records into file in turbo-pascal???

It is because you have misunderstood something.

A string is not a simple POD type -- it is an object type -- which you cannot write directly to file (according to Delphi standards [and also ISO standards, but that's beside the point

]).

The write[ln] functions know how to transform a string into a simple sequence of characters.

They do not know how to handle your thing type, because it has a non-POD member (the string).

When you create file types, they must be sequences of non-object types. Hence, type tFooFile: file of string; fails, where

Pascal Syntax (Toggle Plain Text)
type
  string80: array[ 1..80 ] of char;
  tFooFile: file of string80;
type
  string80: array[ 1..80 ] of char;
  tFooFile: file of string80;

succeeds.

What you can do is write procedures/methods that know how to write your non-POD type to a given file, then call it when you wish to write it.

For more information, google around "delphi or pascal object serialization".

Hope this helps.

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