find() doesn't support multiple conditions

[milktrader]

julia> a = [1:10];

julia> find(a .> 5)
5-element Array{Int64,1}:
  6
  7
  8
  9
 10

julia> find(a .> 5 & a .< 9)
7-element Array{Int64,1}:
  2
  3
  6
  7
  8
  9
 10

julia> find(a .< 9 & a .> 5)
0-element Array{Int64,1}

[milktrader]

#4127

[jiahao]

I think this is an operator precedence issue:

julia> find((a.>5) & (a .<9))
3-element Array{Int64,1}:
 6
 7
 8

julia> find (5.<a.<9)
3-element Array{Int64,1}:
 6
 7
 8

[milktrader]

Oh, cool. I'm not sure if matlab behaves this way but I'm glad we have this available. Thanks!

[ViralBShah]

What would be great is if find can take an expression and evaluate it over the input, instead of forming the intermediate temporary array.

[rickhg12hs]

@ViralBShah : You mean like: ???

julia> a=[1:10]
10-element Array{Int32,1}:
  1
  2
  3
  4
  5
  6
  7
  8
  9
 10

julia> a[(a.<9)&(a.>5)]
3-element Array{Int32,1}:
 6
 7
 8

[ViralBShah]

This creates several temporaries too under the hood.

[rickhg12hs]

@ViralBShah There's still a lot of mystery under the bonnet for me. How does filter fit in-the-mix here?

[mbauman]

This is #5187. I've been thinking I'd bump it at the start of the .4 cycle and champion it a bit more loudly. I'd really like to be able to write multiple conditions without parentheses.