# Generate nested for loops using metaprogramming?
**URL:** https://discourse.julialang.org/t/generate-nested-for-loops-using-metaprogramming/8247
**Category:** General Usage
**Tags:** question, metaprogramming
**Created:** [January 9, 2018, 3:54pm UTC](https://discourse.julialang.org/t/generate-nested-for-loops-using-metaprogramming/8247 "2018-01-09T15:54:47Z")
**Posts on this page:** 5
**Page:** 1
### Author:  [@onetonfoot](https://discourse.julialang.org/u/onetonfoot)
#### Post date: [January 9, 2018, 3:54pm UTC](https://discourse.julialang.org/t/generate-nested-for-loops-using-metaprogramming/8247/1 "2018-01-09T15:54:47Z")
Given a set of characters and a number I’m trying to generate all possible sequences. For example, given
“ACTG” to generate all possible sequences of length 2 I could do.
```julia
letters = "ACTG"
for i in letters
for j in letters
print(i,j," ")
end
end
AA AC AT AG CA CC CT CG TA TC TT TG GA GC GT GG
```
And say n = 3 I could do
```julia
for i in letters
for j in letters
for k in letters
print(i,j,k," ")
end
end
end
```
My question is how can I do this with Julia’s metaprogramming?
---
### Author:  [@rdeits](https://discourse.julialang.org/u/rdeits)
#### Post date: [January 9, 2018, 4:12pm UTC](https://discourse.julialang.org/t/generate-nested-for-loops-using-metaprogramming/8247/2 "2018-01-09T16:12:27Z")
Check out `@nloops`: [https://docs.julialang.org/en/release-0.6/devdocs/cartesian/#Base.Cartesian-1](https://docs.julialang.org/en/release-0.6/devdocs/cartesian/#Base.Cartesian-1)
---
### Author:  [@rdeits](https://discourse.julialang.org/u/rdeits)
#### Post date: [January 9, 2018, 4:14pm UTC](https://discourse.julialang.org/t/generate-nested-for-loops-using-metaprogramming/8247/3 "2018-01-09T16:14:21Z")
Although if you’re actually just trying to generate a product of sequences, then `Iterators.product` will be easier:
```julia
julia> for (i, j) in Iterators.product("ACTG", "ACTG")
print(i, j, " ")
end
AA CA TA GA AC CC TC GC AT CT TT GT AG CG TG GG
```
---
### Author:  [@onetonfoot](https://discourse.julialang.org/u/onetonfoot)
#### Post date: [January 9, 2018, 4:20pm UTC](https://discourse.julialang.org/t/generate-nested-for-loops-using-metaprogramming/8247/4 "2018-01-09T16:20:06Z")
Thanks, that’s way simpler. I’ll have a go at solving it with @nloops for the fun anyways.
---
### Author:  [@onetonfoot](https://discourse.julialang.org/u/onetonfoot)
#### Post date: [June 7, 2018, 3:20pm UTC](https://discourse.julialang.org/t/generate-nested-for-loops-using-metaprogramming/8247/5 "2018-06-07T15:20:39Z")
Half a year later I did it lol.
```julia
function permutations(array,n)
exp = quote
l = []
@nloops $n i _ -> 1:length($array) begin
idx =[@ntuple($n,i)...]
push!(l,$array[idx])
end
l
end
eval(exp)
end
```