如何制作任意级别的嵌套for循环 [英] How to make arbitrary level of nested for-loop
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问题描述
I can do a two level nested loop like this
for i1 in 1:n
for i2 in 1:n
do something with (i1,i2)
How do I extend this into arbitrary level of nested loop?
For example, I can do this in Python to loop the cartesian product of n^m
for i in (itertools.product(xrange(n),repeat=m)):
Like
for i in (itertools.product(xrange(2),repeat=3)):
print i
(0, 0, 0)
(0, 0, 1)
(0, 1, 0)
(0, 1, 1)
(1, 0, 0)
(1, 0, 1)
(1, 1, 0)
(1, 1, 1)
Thank you for @tholy's comment. I have successfully applied Iterators.jl. I'm a Julia newbie so my code maybe clumsy.
for i in product(repmat(Any[1:2],3)...)
println(i)
end
(1,1,1)
(2,1,1)
(1,2,1)
(2,2,1)
(1,1,2)
(2,1,2)
(1,2,2)
(2,2,2)
解决方案
In v0.5 there is a product iterator in Base, so you can now write this as Base.product(fill(1:2,3)...)
. fill
produces an array with a value repeated some number of times; I find this a bit more elegant than creating a 1-element array and calling repmat
.
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