Ahammell wrote at Wed, 12 Jun 2002 05:32:19 +0200:
> Janek Schleicher wrote:
>> It's a real crime to copy source code.
I missed to say :-). Sorry.
>> Here you see why.
>>
>> Cheerio,
>> Janek
>>
>>
> Janek,
> Im sorry but I dont quite understand your statements. I sincerely hope
> that you are not accusing me of copying source code. I truly dont know why you would
>think that
> and if you dont I apologize for this part of my response. I simply posted with a
>question about my
> source code that I thought someone could help with.
>
I didn't mean that it is a crime to copy source code from another program.
I mean't it is very dangerous to program with a copy+paste style.
Why? First of all, if you have to make a change later,
then you should only have to change the code at ONE position.
There's also a great danger that little errors are done by copying+paste.
The source code posted here, showed some of the little errors:
> > if ($href->{st_name1} eq "$state") {
> > #print "$href->{quad_name}, $href->{st_name1}\n" ;
> > $state_hash{"$href->{quad_name}"} = "$href->{st_name1}" ;
> ^
> > }
> > }
> > elsif ($href->{st_name2} eq "$state") {
> > #print "$href->{quad_name}, $href->{st_name1}\n" ;
> > $state_hash{"$href->{quad_name}"} = "$href->{st_name1}" ;
^
As you can see, both if-constructs are nearly the same.
In fact there's only one character different (st_name1 <=> st_name2).
The constructs make only sense when in the assignment
the 1 is replaced by 2.
Such little mistakes are typical for copying+paste - programming.
It seems, that the author wanted to say:
set the state of the hyperlink reference to quad_name to
the reference of st_nameX, where the reference to st_nameX is the $state.
Instead of that, the code says something like:
set the state ... of quadname ... to st_name1 if reference of st_name1 eq $state
set the state ... of quadname ... to st_name2 if reference of st_name2 eq $state
set the state ... of quadname ... to st_name3 if reference of st_name3 eq $state
set the state ... of quadname ... to st_name4 if reference of st_name4 eq $state
As you can see, the real idea is hidden.
That's an alert signal.
Well, you could say, I have to be more carefully when copying.
I should write a short comment to explain the idea.
But that's not the way. You'll become a better programmer avoiding doubled code.
(Or just take BASIC - use goto; peek; poke; and randomness line numbering)
Doubled code have a similar functionality -
that's why write a loop, subroutine, module, class, macro or use Perl's powerful eval.
Of course it needs a little time -
but you get it back later (with factor 3).
As in the example above - you also could write a pseudocode like:
foreach X (1 .. 4)
set the state of the hyperlink reference to quad_name to
the reference of st_nameX, if the reference to st_nameX is the $state.
what should be possible to implement.
I know it's hard, always to remember that I shouldn't copy code.
In addition it's hard, when you're a programming newbie.
So I always say - and that's simple to remember -
that it is a real crime to copy code.
Cheerio,
Janek
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