allow range(start, stop; ...)

finishes #25896

Author: JeffBezanson

base/range.jl

@@ -46,7 +46,7 @@ function _colon(start::T, step, stop::T) where T
 end
 
 """
-    range(start; length, stop, step=1)
+    range(start[, stop]; 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)).
@@ -58,6 +58,8 @@ 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 (a [`StepRange`](@ref)).
 
+`stop` may be specified as either a positional or keyword argument.
+
 # Examples
 ```jldoctest
 julia> range(1, length=100)
@@ -71,11 +73,28 @@ julia> range(1, step=5, length=100)
 
 julia> range(1, step=5, stop=100)
 1:5:96
+
+julia> range(1, 100)
+1:100
+
+julia> range(1, 10, length=101)
+1.0:0.09:10.0
+
+julia> range(1, 100, step=5)
+1:5:96
 ```
 """
 range(start; length::Union{Integer,Nothing}=nothing, stop=nothing, step=nothing) =
     _range(start, step, stop, length)
 
+range(start, stop; length::Union{Integer,Nothing}=nothing, step=nothing) =
+    _range2(start, step, stop, length)
+
+_range2(start, ::Nothing, stop, ::Nothing) =
+    throw(ArgumentError("At least one of `length` or `step` must be specified"))
+
+_range2(start, step, stop, length) = _range(start, step, stop, length)
+
 # Range from start to stop: range(a, [step=s,] stop=b), no length
 _range(start, step,      stop, ::Nothing) = (:)(start, step, stop)
 _range(start, ::Nothing, stop, ::Nothing) = (:)(start, stop)

test/ranges.jl

@@ -1418,3 +1418,20 @@ end
     @test @allocated(0:286.493442:360) == 0
     @test @allocated(0:286:360) == 0
 end
+
+@testset "range with start and stop" begin
+    for starts in [-1, 0, 1, 10]
+        for stops in [-2, 0, 2, 100]
+            for lengths in [2, 10, 100]
+                if stops >= starts
+                    @test range(starts, stops, length=lengths) == range(starts, stop=stops, length=lengths)
+                end
+            end
+            for steps in [0.01, 1, 2]
+                @test range(starts, stops, step=steps) == range(starts, stop=stops, step=steps)
+            end
+        end
+    end
+    # require a keyword arg
+    @test_throws ArgumentError range(1, 100)
+end