# This file is a part of Julia. License is MIT: https://julialang.org/license
# `ntuple`, for constructing tuples of a given length
"""
ntuple(f, n::Integer)
Create a tuple of length `n`, computing each element as `f(i)`,
where `i` is the index of the element.
# Examples
```jldoctest
julia> ntuple(i -> 2*i, 4)
(2, 4, 6, 8)
```
"""
@inline function ntuple(f::F, n::Integer) where F
# marked inline since this benefits from constant propagation of `n`
t = n == 0 ? () :
n == 1 ? (f(1),) :
n == 2 ? (f(1), f(2)) :
n == 3 ? (f(1), f(2), f(3)) :
n == 4 ? (f(1), f(2), f(3), f(4)) :
n == 5 ? (f(1), f(2), f(3), f(4), f(5)) :
n == 6 ? (f(1), f(2), f(3), f(4), f(5), f(6)) :
n == 7 ? (f(1), f(2), f(3), f(4), f(5), f(6), f(7)) :
n == 8 ? (f(1), f(2), f(3), f(4), f(5), f(6), f(7), f(8)) :
n == 9 ? (f(1), f(2), f(3), f(4), f(5), f(6), f(7), f(8), f(9)) :
n == 10 ? (f(1), f(2), f(3), f(4), f(5), f(6), f(7), f(8), f(9), f(10)) :
_ntuple(f, n)
return t
end
function _ntuple(f::F, n) where F
@noinline
(n >= 0) || throw(ArgumentError(LazyString("tuple length should be ≥ 0, got ", n)))
([f(i) for i = 1:n]...,)
end
function ntupleany(f, n)
@noinline
(n >= 0) || throw(ArgumentError(LazyString("tuple length should be ≥ 0, got ", n)))
(Any[f(i) for i = 1:n]...,)
end
# inferable ntuple (enough for bootstrapping)
ntuple(f, ::Val{0}) = ()
ntuple(f, ::Val{1}) = (@inline; (f(1),))
ntuple(f, ::Val{2}) = (@inline; (f(1), f(2)))
ntuple(f, ::Val{3}) = (@inline; (f(1), f(2), f(3)))
"""
ntuple(f, ::Val{N})
Create a tuple of length `N`, computing each element as `f(i)`,
where `i` is the index of the element. By taking a `Val(N)`
argument, it is possible that this version of ntuple may
generate more efficient code than the version taking the
length as an integer. But `ntuple(f, N)` is preferable to
`ntuple(f, Val(N))` in cases where `N` cannot be determined
at compile time.
# Examples
```jldoctest
julia> ntuple(i -> 2*i, Val(4))
(2, 4, 6, 8)
```
"""
@inline function ntuple(f::F, ::Val{N}) where {F,N}
N::Int
(N >= 0) || throw(ArgumentError(LazyString("tuple length should be ≥ 0, got ", N)))
if @generated
:(@ntuple $N i -> f(i))
else
Tuple(f(i) for i = 1:N)
end
end
@inline function fill_to_length(t::Tuple, val, ::Val{_N}) where {_N}
M = length(t)
N = _N::Int
M > N && throw(ArgumentError(LazyString("input tuple of length ", M, ", requested ", N)))
if @generated
quote
(t..., $(fill(:val, (_N::Int) - length(t.parameters))...))
end
else
(t..., fill(val, N-M)...)
end
end