# Nested for-loops, there has to be a better way to do this

Yves S. Garret yoursurrogategod@REDACTED
Fri Jul 31 04:05:54 CEST 2009

```Oh, that looks cool.  Thanks for sharing.

On Jul 30, 5:46 am, Robert Raschke <rtrli...@REDACTED> wrote:
> On Wed, Jul 29, 2009 at 10:08 PM, Fred Hebert (MononcQc) <monon...@REDACTED
>
>
>
>
>
> > wrote:
> > I find nested lists comprehension to be the easiest to deal with when
> > representing nested loops:
>
> > [[ Fn(I,J) || J <- GenExp2 ] || I <- GenEXp1 ].
>
> > or indented in a different way:
>
> >  [[[ Fn(I, J, K) || K <- GenExp3 ]
> >                 || J <- GenExp2 ]
> >                 || I <- GenExp1 ].
>
> > This gives a nested list. If that's not what you want, you could use
> > lists:flatten/1 to change that, but overall I find this form to be the
> > cleanest (visually speaking).
>
> I may be missing something obvious, but ...
>
> 1> [ {A,B,C,A+B+C} || A<-lists:seq(1,5), B<-lists:seq(1,5),
> C<-lists:seq(1,10) ].
> [{1,1,1,3},
>  {1,1,2,4},
>  {1,1,3,5},
>  {1,1,4,6},
>  {1,1,5,7},
>  {1,1,6,8},
>  {1,1,7,9},
>  {1,1,8,10},
>  {1,1,9,11},
>  {1,1,10,12},
>  {1,2,1,4},
>  {1,2,2,5},
>  {1,2,3,6},
>  {1,2,4,7},
>  {1,2,5,8},
>  {1,2,6,9},
>  {1,2,7,10},
>  {1,2,8,11},
>  {1,2,9,12},
>  {1,2,10,13},
>  {1,3,1,5},
>  {1,3,2,6},
>  {1,3,3,7},
>  {1,3,4,8},
>  {1,3,5,9},
>  {1,3,6,...},
>  {1,3,...},
>  {1,...},
>  {...}|...]
> 2>
>
> Robby
```