Unexpected behaviour of broadcast getindex.() if there are slices

[MoonCoral]

Toy Example:
(Tested in 0.6 and 0.7-beta.0)

 # Nested Array
input = [
    [1, 2, 3, 4, 5, 6, 7, 8, 9],
    [10, 20, 30, 40, 50, 60, 70, 80, 90],
    [100, 200, 300, 400, 500, 600, 700, 800, 900]
]

# For reference, this does what I expect
output = getindex.(input, 3)
# 3-element Array{Int64,1}:
# 3
# 30
# 300

# Unexpected Output
output = getindex.(input, 4:6)
# 3-element Array{Int64,1}:
# 4
# 50
# 600

# What I expected to be returned
output = [getindex(input[1], 4:6), getindex(input[2], 4:6), getindex(input[3], 4:6)]
# 3-element Array{Array{Int64,1},1}:
# [4, 5, 6]      
# [40, 50, 60]   
# [400, 500, 600]

# This Errors
output = getindex.(input, 4:7)
# ERROR: DimensionMismatch("arrays could not be broadcast to a common size")

# What I expected to be returned
output = [getindex(input[1], 4:7), getindex(input[2], 4:7), getindex(input[3], 4:7)]
# 3-element Array{Array{Int64,1},1}:
# [4, 5, 6, 7]        
# [40, 50, 60, 70]    
# [400, 500, 600, 700]

Based on the above I assume, that the ranges are not passed verbatim by broadcast to the getindex function. But instead are expanded and participate in the broadcast.

My question now is, is this the desired behaviour and if so is there any non-verbose syntax to achieve what I want assuming I don't know the size of input beforehand and do not want to write a for loop as it interrupts broadcast chaining?

Edit: The current behaviour seems to be that of broadcast_getindex (getting deprecated in favour of the syntax in question in #27075).

[stevengj]

Based on the above I assume, that the ranges are not passed verbatim by broadcast to the getindex function. But instead are expanded and participate in the broadcast.

Range arguments are treated as arrays (they are AbstractArrays) and are broadcasted over, whereas in this case you want them treated as "scalars" (i.e. not broadcasted over). You can suppress this with Ref or `RefValue:

julia> output = getindex.(input, Base.RefValue(4:6))
3-element Array{Array{Int64,1},1}:
 [4, 5, 6]      
 [40, 50, 60]   
 [400, 500, 600]

(Base.RefValue is a bit annoying here; see also #27608 for a possibly better syntax in the future.)

[stevengj]

Closing as this is not a bug.

[MoonCoral]

Thank you for clarifying this and your advise.