Re: [wxperl-users] declarative syntax

[Eric W. <scr...@gm...>]

# from Sergei Steshenko
# on Sunday 18 March 2007 02:15 pm:

>funky_array =3D> [1, 2, 3, 5, 8 ...],
># element is the some of previous two,
># and this way 100 times;=20

>So, this is Perl, and there is more than one to do it, and I would do
> it this way:
>
>{
>...
>funky_array =3D> do{
>=A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0my @tmp_array; =A0# no name clash dange=
r, the scope
>=A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0# =A0pr=
otects from name contention
>
>=A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0my $number_of_times =3D 100; # I said 1=
00 times, dodn't
> I ?
>
>=A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0my $previous_element =3D 0;
>=A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0my $element =3D 1;
>
>=A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0while($number_of_times-- > 0)
>=A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0{
>=A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0$element +=3D $previous_element;
>=A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0push @tmp_array, $element;
>=A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0$previous_element =3D $element;
>=A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0}
>
>=A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0\@tmp_array; # the array reference to b=
e returned
>=A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0}
>};
>
>So, the point of this example is that there should be
> canonical/normalized data structure and there can be infinite number
> of ways to produce it.

=46ine.  But, you should be able to skim over the code in much less space. =
=20
When you want to build something based on a rolling pair of values, why=20
not use a rolling pair of values?

  ...
  funky_array =3D> do {my @p =3D (1,2);
    [1,2,map({push(@p, my $v =3D shift(@p)+$p[0]); $v} 3..100)]},
  ...

And once you know it is correct, you don't have to read it.  Of course,=20
I would put that in a method call and maybe even test that it gave the=20
correct answer.

And as far as understanding what it does.  With a little examination, it=20
is fairly clear that it doesn't do:

  ...
  funky_array =3D> [map({2**$_} 0..99)],
  ...

Thanks for helping to illustrate my point.  More code means more bugs. =20
Individual line complexity really doesn't mean much.  Bug density has=20
been shown to be roughly a constant proportion of SLOC across multiple=20
languages.

=2D-Eric
=2D-=20
perl -e 'srand; print join(" ",sort({rand() < 0.5}
  qw(sometimes it is important to be consistent)));'
=2D--------------------------------------------------
    http://scratchcomputing.com
=2D--------------------------------------------------