# Efficient Repeat: Array of single value
**URL:** https://discourse.julialang.org/t/efficient-repeat-array-of-single-value/55464
**Category:** New to Julia
**Created:** [February 17, 2021, 2:40pm UTC](https://discourse.julialang.org/t/efficient-repeat-array-of-single-value/55464 "2021-02-17T14:40:47Z")
**Posts on this page:** 4
**Page:** 1
### Author:  [@bgctw](https://discourse.julialang.org/u/bgctw)
#### Post date: [February 17, 2021, 2:40pm UTC](https://discourse.julialang.org/t/efficient-repeat-array-of-single-value/55464/1 "2021-02-17T14:40:47Z")
I want to define defaults for a read-only `AbstractVector{Bool}` argument to a function and so far used `falses(n)`. However, this allocates a full `BitArray`.
I guess should be a type similar to a `Range` that can do this job, similar to:
```julia
struct Repeat{T,N} end
Base.getindex(r::Repeat{T,N},i::Int) where {T,N} =
(1 <= i <= N) ? T : throw(BoundsError(r,i))
Base.length(r::Repeat{T,N}) where {T,N} = N
```
Before I invest much time in developing such a type with the full Array interface, I ask how such cases are handled so far in Julia?
---
### Author:  [@jipolanco](https://discourse.julialang.org/u/jipolanco)
#### Post date: [February 17, 2021, 2:57pm UTC](https://discourse.julialang.org/t/efficient-repeat-array-of-single-value/55464/2 "2021-02-17T14:57:36Z")
You can use [FillArrays.jl](https://github.com/JuliaArrays/FillArrays.jl) for this:
```julia
julia> using FillArrays
julia> x = Fill(false, 10)
10-element Fill{Bool}: entries equal to false
julia> x[3]
false
julia> x[11]
ERROR: BoundsError: attempt to access 10-element Fill{Bool} at index [11]
Stacktrace:
[1] throw_boundserror(A::Fill{Bool, 1, Tuple{Base.OneTo{Int64}}}, I::Tuple{Int64})
@ Base ./abstractarray.jl:645
[2] checkbounds
@ ./abstractarray.jl:610 [inlined]
[3] getindex(F::Fill{Bool, 1, Tuple{Base.OneTo{Int64}}}, kj::Int64)
@ FillArrays ~/.julia/packages/FillArrays/FPGoE/src/FillArrays.jl:41
[4] top-level scope
@ REPL[11]:1
```
---
### Author:  [@Henrique\_Becker](https://discourse.julialang.org/u/Henrique_Becker)
#### Post date: [February 17, 2021, 2:58pm UTC](https://discourse.julialang.org/t/efficient-repeat-array-of-single-value/55464/3 "2021-02-17T14:58:25Z")
Something close to what you want already exists (in Base):
```julia
help?> Iterators.repeated
repeated(x[, n::Int])
An iterator that generates the value x forever. If n is specified, generates x
that many times (equivalent to take(repeated(x), n)).
Examples
≡≡≡≡≡≡≡≡≡≡
julia> a = Iterators.repeated([1 2], 4);
julia> collect(a)
4-element Array{Array{Int64,2},1}:
[1 2]
[1 2]
[1 2]
[1 2]
```
I checked and it supports `length`. However, it does not support indexing (i.e., `a[1]` will fail). ~~Did you search for packages, I find strange nobody implemented that.~~ As @jipolanco pointed out this already exists.
Also, I would not recommend putting the length in a type parameter of the struct, otherwise your code will be re-compiled each time you pass a `Repeat` of different size to your functions. `StaticArrays` does this for very small and “often the same size” objects.
---
### Author:  [@bgctw](https://discourse.julialang.org/u/bgctw)
#### Post date: [February 17, 2021, 6:17pm UTC](https://discourse.julialang.org/t/efficient-repeat-array-of-single-value/55464/4 "2021-02-17T18:17:26Z")
`typeof(Falses(4)) <: AbstractArray{Bool}`
perfect, Thank you.