# Base.product repeat 1:2 5 times
**URL:** https://discourse.julialang.org/t/base-product-repeat-1-2-5-times/16642
**Category:** General Usage
**Created:** [October 22, 2018, 6:02pm UTC](https://discourse.julialang.org/t/base-product-repeat-1-2-5-times/16642 "2018-10-22T18:02:56Z")
**Posts on this page:** 5
**Page:** 1
### Author:  [@Paul\_McVay](https://discourse.julialang.org/u/Paul_McVay)
#### Post date: [October 22, 2018, 6:02pm UTC](https://discourse.julialang.org/t/base-product-repeat-1-2-5-times/16642/1 "2018-10-22T18:02:56Z")
For the Base.product function, is there a simple way to repeat the input array 1:2 5 times? So for example, instead of having to type
```julia
Base.product(1:2, 1:2, 1:2, 1:2, 1:2)
```
Be able to type
```julia
Base.product(repeat(1:2, 5))
```
---
### Author:  [@carstenbauer](https://discourse.julialang.org/u/carstenbauer)
#### Post date: [October 22, 2018, 6:17pm UTC](https://discourse.julialang.org/t/base-product-repeat-1-2-5-times/16642/2 "2018-10-22T18:17:06Z")
You could (but shouldn’t) write
```julia
Base.product(fill(1:2, 5)...)
```
This will be much slower as it creates an intermediate array:
```julia
julia> @btime Base.product(1:2, 1:2, 1:2, 1:2, 1:2)
2.133 ns (0 allocations: 0 bytes)
Base.Iterators.ProductIterator{NTuple{5,UnitRange{Int64}}}((1:2, 1:2, 1:2, 1:2, 1:2))
julia> @btime Base.product(fill(1:2, 5)...)
521.232 ns (8 allocations: 512 bytes)
Base.Iterators.ProductIterator{NTuple{5,UnitRange{Int64}}}((1:2, 1:2, 1:2, 1:2, 1:2))
```
If you really want to write less and keep performance you could use a macro I guess.
---
### Author:  [@favba](https://discourse.julialang.org/u/favba)
#### Post date: [October 22, 2018, 6:18pm UTC](https://discourse.julialang.org/t/base-product-repeat-1-2-5-times/16642/3 "2018-10-22T18:18:18Z")
This is what I came up with
```julia
Base.product(ntuple(i->1:2,Val{5}())...)
```
```julia
julia> using BenchmarkTools
julia> @btime Base.product(1:2, 1:2, 1:2, 1:2, 1:2)
2.145 ns (0 allocations: 0 bytes)
Base.Iterators.ProductIterator{NTuple{5,UnitRange{Int64}}}((1:2, 1:2, 1:2, 1:2, 1:2))
julia> @btime Base.product(fill(1:2, 5)...)
580.244 ns (8 allocations: 512 bytes)
Base.Iterators.ProductIterator{NTuple{5,UnitRange{Int64}}}((1:2, 1:2, 1:2, 1:2, 1:2))
julia> @btime Base.product(ntuple(i->1:2,Val{5}())...)
2.144 ns (0 allocations: 0 bytes)
Base.Iterators.ProductIterator{NTuple{5,UnitRange{Int64}}}((1:2, 1:2, 1:2, 1:2, 1:2))
```
---
### Author:  [@Paul\_McVay](https://discourse.julialang.org/u/Paul_McVay)
#### Post date: [October 22, 2018, 6:34pm UTC](https://discourse.julialang.org/t/base-product-repeat-1-2-5-times/16642/4 "2018-10-22T18:34:41Z")
Just out of curiosity (I’m new to julia), what do you use `Val{5}()`? I get the same performance with just `5`
---
### Author:  [@favba](https://discourse.julialang.org/u/favba)
#### Post date: [October 22, 2018, 6:56pm UTC](https://discourse.julialang.org/t/base-product-repeat-1-2-5-times/16642/5 "2018-10-22T18:56:47Z")
That is to guarantee that the length of the tuple will be known at compile time.
With constant propagation it might be that using `5` directly will still work as performant as with using `Val{5}()`, but it is not guaranteed.
For ex:
```julia
julia> using BenchmarkTools
julia> function g(n)
l = Base.product(ntuple(i->1:2,n)...)
x = 0
for i in l
x+=1
end
return x
end
g (generic function with 1 method)
julia> @btime g(5)
2.611 μs (72 allocations: 7.44 KiB)
32
julia> @btime g(Val{5}())
27.610 ns (0 allocations: 0 bytes)
32
```