Add range(start, stop) and range(start, stop, length) (JuliaLang#39228)

* Add range(start, stop) and range(start, stop, length)

Co-authored-by: Matt Bauman <mbauman@juliacomputing.com>

NEWS.md

@@ -43,6 +43,7 @@ Standard library changes
 ------------------------
 
 * `count` and `findall` now accept an `AbstractChar` argument to search for a character in a string ([#38675]).
+* `range` now supports the `range(start, stop)` and `range(start, stop, length)` methods ([#39228]).
 * `range` now supports `start` as an optional keyword argument ([#38041]).
 * `islowercase` and `isuppercase` are now compliant with the Unicode lower/uppercase categories ([#38574]).
 * `iseven` and `isodd` functions now support non-`Integer` numeric types ([#38976]).

base/range.jl

@@ -47,6 +47,7 @@ function _colon(start::T, step, stop::T) where T
 end
 
 """
+    range(start, stop, length)
     range(start, stop; length, step)
     range(start; length, stop, step)
     range(;start, length, stop, step)
@@ -96,34 +97,19 @@ julia> range(1, 3.5, step=2)
 Special care is taken to ensure intermediate values are computed rationally.
 To avoid this induced overhead, see the [`LinRange`](@ref) constructor.
 
-Both `start`  and `stop` may be specified as either a positional or keyword arguments.
-If both are specified as positional arguments, one of `step` or `length` must also be provided.
-
 !!! compat "Julia 1.1"
     `stop` as a positional argument requires at least Julia 1.1.
 
 !!! compat "Julia 1.7"
-    `start` as a keyword argument requires at least Julia 1.7.
+    The versions without keyword arguments and `start` as a keyword argument
+    require at least Julia 1.7.
 """
 function range end
 
 range(start; stop=nothing, length::Union{Integer,Nothing}=nothing, step=nothing) =
     _range(start, step, stop, length)
-
-function range(start, stop; length::Union{Integer,Nothing}=nothing, step=nothing)
-    # For code clarity, the user must pass step or length
-    # See https://github.com/JuliaLang/julia/pull/28708#issuecomment-420034562
-    if step === length === nothing
-        msg = """
-        Neither `step` nor `length` was provided. To fix this do one of the following:
-        * Pass one of them
-        * Use `$(start):$(stop)`
-        * Use `range($start, stop=$stop)`
-        """
-        throw(ArgumentError(msg))
-    end
-    _range(start, step, stop, length)
-end
+range(start, stop; length::Union{Integer,Nothing}=nothing, step=nothing) = _range(start, step, stop, length)
+range(start, stop, length::Integer) = _range(start, nothing, stop, length)
 
 range(;start=nothing, stop=nothing, length::Union{Integer, Nothing}=nothing, step=nothing) =
     _range(start, step, stop, length)

test/ranges.jl

@@ -1,26 +1,26 @@
 # This file is a part of Julia. License is MIT: https://julialang.org/license
 
 @testset "range construction" begin
-    @testset "range(;kw...)" begin
-        @test_throws ArgumentError range(start=1, step=1, stop=2, length=10)
-        @test_throws ArgumentError range(start=1, step=1, stop=10, length=11)
-
-        r = 3.0:2:11
-        @test r == range(start=first(r), step=step(r), stop=last(r)                  )
-        @test r == range(start=first(r), step=step(r),               length=length(r))
-        @test r == range(start=first(r),               stop=last(r), length=length(r))
-        @test r == range(                step=step(r), stop=last(r), length=length(r))
-
-        r = 4:9
-        @test r === range(start=first(r), stop=last(r)                  )
-        @test r === range(start=first(r),               length=length(r))
-        # the next one uses ==, because it changes the eltype
-        @test r  == range(start=first(r), stop=last(r), length=length(r))
-        @test r === range(                stop=last(r), length=length(r))
-
-        for T = (Int8, Rational{Int16}, UInt32, Float64, Char)
-            @test typeof(range(start=T(5), length=3)) === typeof(range(stop=T(5), length=3))
-        end
+    @test_throws ArgumentError range(start=1, step=1, stop=2, length=10)
+    @test_throws ArgumentError range(start=1, step=1, stop=10, length=11)
+
+    r = 3.0:2:11
+    @test r == range(start=first(r), step=step(r), stop=last(r)                  )
+    @test r == range(start=first(r), step=step(r),               length=length(r))
+    @test r == range(start=first(r),               stop=last(r), length=length(r))
+    @test r == range(                step=step(r), stop=last(r), length=length(r))
+
+    r = 4:9
+    @test r === range(start=first(r), stop=last(r)                  )
+    @test r === range(start=first(r),               length=length(r))
+    @test r === range(                stop=last(r), length=length(r))
+    @test r === range(first(r),       last(r)                       )
+    # the next ones use ==, because it changes the eltype
+    @test r ==  range(first(r),       last(r),      length(r)       )
+    @test r ==  range(start=first(r), stop=last(r), length=length(r))
+
+    for T = (Int8, Rational{Int16}, UInt32, Float64, Char)
+        @test typeof(range(start=T(5), length=3)) === typeof(range(stop=T(5), length=3))
     end
 end
 
@@ -1630,8 +1630,6 @@ end
             end
         end
     end
-    # require a keyword arg
-    @test_throws ArgumentError range(1, 100)
 end
 
 @testset "Reverse empty ranges" begin