[erlang-questions] Nested for-loops, there has to be a better way to do this

Richard O'Keefe <>
Wed Jul 29 05:32:50 CEST 2009


On Jul 29, 2009, at 2:55 PM, Yves S. Garret wrote:

> I was playing around with the idea of implementing a nested for- 
> loop... a
> list [5, 5, 10] (for example) and go through it all like 3 dimensional
> array.

I don't understand what it is you want to do.
Will something like
	D1 = lists:seq(1, 5),
	D2 = lists:seq(1, 5),
	D3 = lists:seq(1, 10),
	% do this for effect, not result
	[ effect(I1, I2, I3) || I1 <- D1, I2 <- D2, I3 <- D3 ]
do what you want?

I've been playing with a syntax that allows, amongst other
special cases,
	( effect(I1, I2, I3) || I1 <- D1, I2 <- D2, I3 <- D3 )
However, it's not really needed; all that's needed is for the
Erlang compiler to notice that the result of a list comprehension
is not being used, and just not bother constructing the result.




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