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Add range(start, stop, length) #39055

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Add range(start, stop, length) #39055

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68dbb1d
Add range(start, stop, length)
mkitti Dec 30, 2020
fb1dad1
Add tests for range(start, stop, length)
mkitti Jan 4, 2021
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10 changes: 9 additions & 1 deletion base/range.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -47,7 +47,7 @@ function _colon(start::T, step, stop::T) where T
end

"""
range(start[, stop]; length, stop, step=1)
range(start[, stop[, length]]; length, stop, step=1)

Given a starting value, construct a range either by length or from `start` to `stop`,
optionally with a given step (defaults to 1, a [`UnitRange`](@ref)).
Expand All @@ -59,6 +59,8 @@ automatically such that there are `length` linearly spaced elements in the range
If `step` and `stop` are provided and `length` is not, the overall range length will be computed
automatically such that the elements are `step` spaced.

If `start`, `stop`, and `length` are specified by position, no keywords are permitted.

Special care is taken to ensure intermediate values are computed rationally.
To avoid this induced overhead, see the [`LinRange`](@ref) constructor.

Expand All @@ -84,6 +86,9 @@ julia> range(1, step=5, stop=100)
julia> range(1, 10, length=101)
1.0:0.09:10.0

julia> range(1, 10, 101)
1.0:0.09:10.0

julia> range(1, 100, step=5)
1:5:96
```
Expand All @@ -94,6 +99,9 @@ range(start; length::Union{Integer,Nothing}=nothing, stop=nothing, step=nothing)
range(start, stop; length::Union{Integer,Nothing}=nothing, step=nothing) =
_range2(start, step, stop, length)

range(start, stop, length::Union{Integer,Nothing}) =
_range(start, nothing, stop, length)

_range2(start, ::Nothing, stop, ::Nothing) =
throw(ArgumentError("At least one of `length` or `step` must be specified"))

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11 changes: 11 additions & 0 deletions test/ranges.jl
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Expand Up @@ -1610,6 +1610,17 @@ end
@test_throws ArgumentError range(1, 100)
end

@testset "range wtih start, stop, and length" begin
for starts in [-1, 0, 1, 10]
for stops in [-2, 0, 2, 100]
for lengths in [2, 10, 100]
@test range(starts, stops, lengths) === range(starts, stop=stops, length=lengths)
end
@test range(starts, stops, nothing) === range(starts, stop=stops)
end
end
end

@testset "Reverse empty ranges" begin
@test reverse(1:0) === 0:-1:1
@test reverse(Base.OneTo(0)) === 0:-1:1
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