[fpc-pascal] accessing files from a function

[johnelee1944 at googlemail.com]

thanks all - btw it wasn't the real code just an example I made up , the  
while loop wasn't needed- mistake!

But the q still remains - having three functions would still give the  
problem I have now- that when doing a file_read (my function flag=1) would  
say 'file not open' because the handles are volatile & local to file reset  
- that was the point of my original email. Seems as if there is no solution?
John


On , Rainer Stratmann <RainerStratmann at t-online.de> wrote:
> In my eyes it is (very) unlogic.



> Why don't you make 3 functions?

> Something like this...



> var filename : string; // global var for storing the filename



> function file_reset( name : string ) : boolean;

> function file_read( var eof : boolean ) : string;

> function file_close : boolean;



> Whith your example you don't have to pass the filename for operation 1

> (flag=1).



> Rainer



> Am Monday 16 May 2011 02:28:14 schrieb John Lee:

> > I'd like to put the assign and reset of a text file into a function, and

> > then use the function to return a line from the file, without needing to

> > close the file then re assign and reset every time (for performance

> > reasons) - see below for my attempt.

> >

> > This doesn't work because I guess the file handles etc are local to the

> > function are volatile, so cannot be accessed in the main program Is  
> there

> > a simple way to fix this ie to make this function work. Of course one  
> can

> > const in a function to make normal variables non volatile...but files  
> etc?

> >

> > TIA for any ideas...John

> >

> > main program...

> > get_line('tmp.tmp,0), to assign and reset;

> >

> > {get lines}

> > str1:=get_line('tmp.tmp,1);

> > str2:=get_line('tmp.tmp,1)

> > ....

> > {close)

> > get_line('tmp.tmp,2)

> >

> > assume function is defined as

> > function get_line( fname;string;flag:longint):string;

> > var f:text

> > begin

> > if flag=0 then

> > begin

> > assign(f,fname);

> > reset(f);

> > end;

> > if flag=1 then

> > while not eof(f) do

> > begin

> > readln(f);

> > end;

> >

> > if flag=2 then close(f);

> > get_line;=f;

> > end;





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