Re: Avoiding side effects

[Anders Wirzenius <anders@no.email.thanks.invalid>]

Ole-Hjalmar Kristensen <ole-hjalmar.kristensen@substitute_employer_here.com> writes:

> If I understand your problem correctly, why not simply do the
> following after the sort -u stage?:
> 
> comm -23 fileA fileB

Oops. I was not aware of that program. Looks promising. Thanks.

> 
> But to answer the Ada quiestion, I think I would organize the loop a
> little bit differently. The following is a classical way of merging
> two files, but it should work in your case too:
> 
>   while not End_Of_File(File_A) and not End_Of_File(File_B) loop
>   -- Process records from both files
>   end loop;
> 
>   while not End_Of_File(File_A) loop
>   -- Process tail of file A
>   end loop;
> 
>   while not End_Of_File(File_B) loop
>   -- Process tail of file B
>   end loop;

Thanks for that, too. The program I wrote did the job and was
sufficiently fast. My question was more about how to do it using
subprograms (functions) without side effects. 
I suppose "Process records from..." and "Process tail..." are
having side effects if coded as subprograms, as they advance the
pointer in the two files.

-- 
Anders