Outer product of more than two vectors

General Usage
, ,
6

It’s pretty simple with Iterators.product:

outer_product3(vs) = Base.splat(*).(Iterators.product(vs...))

Also seems to be faster for this small example:

julia> @benchmark outer_product($vs)
BenchmarkTools.Trial: 10000 samples with 6 evaluations.
 Range (min … max):  5.900 μs … 910.300 μs  ┊ GC (min … max): 0.00% … 98.87%
 Time  (median):     6.117 μs               ┊ GC (median):    0.00%
 Time  (mean ± σ):   6.828 μs ±  21.970 μs  ┊ GC (mean ± σ):  7.83% ±  2.42%

   ▆▇█▇▆▆▅▅▄▃▃▂▃▃▂▂▁▂▂▁▂▁ ▁ ▁▁                                ▂
  ████████████████████████████▇█▇█▆▇▇▆▅▆▅▅▅▅▅▅▄▆▅▅▄▅▃▃▄▂▄▆▅▆▅ █
  5.9 μs       Histogram: log(frequency) by time      8.47 μs <

 Memory estimate: 5.11 KiB, allocs estimate: 135.

julia> @benchmark outer_product2($vs)
BenchmarkTools.Trial: 10000 samples with 10 evaluations.
 Range (min … max):  1.530 μs … 488.580 μs  ┊ GC (min … max): 0.00% … 98.97%
 Time  (median):     1.610 μs               ┊ GC (median):    0.00%
 Time  (mean ± σ):   1.756 μs ±   4.889 μs  ┊ GC (mean ± σ):  2.75% ±  0.99%

   ▅█
  ▄███▆▃▃▄▅▅▃▃▂▃▄▃▃▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▁▂▂▁▁▁▂▂▂▁▂▂▁▂▂▂▂▂▁▂ ▃
  1.53 μs         Histogram: frequency by time        2.96 μs <

 Memory estimate: 752 bytes, allocs estimate: 15.

julia> @benchmark outer_product3($vs)
BenchmarkTools.Trial: 10000 samples with 176 evaluations.
 Range (min … max):  605.114 ns …  13.131 μs  ┊ GC (min … max): 0.00% … 92.48%
 Time  (median):     652.841 ns               ┊ GC (median):    0.00%
 Time  (mean ± σ):   707.149 ns ± 606.302 ns  ┊ GC (mean ± σ):  4.17% ±  4.69%

  █▅▃ ▇▆▅▃▂▂▂▁ ▁   ▂▂▂▁   ▁▂▁▁                                  ▂
  █████████████████████▆▇█████▇▇▇▆▆▆▇▆▅▅▆▆▆▁▄▃▄▇█▅▅▅██▅▇▆▆▅▄▆▅▆ █
  605 ns        Histogram: log(frequency) by time       1.28 μs <

 Memory estimate: 672 bytes, allocs estimate: 7.
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