Create reduced set of combinations with nextflow tuple channel

Question

I have a question regarding nextflow and how to process the following channel of tuples and two single elements:

tuple_ch = Channel.of([['a','a','a','a'], 
                       ['B','B','B','B'], 
                       ['m','m','m','m'], 
                       1,2])

How could I transform tuple_ch to look like this (so its now a list of tuples):

[['a','B','m',1,2],
 ['a','B','m',1,2],
 ['a','B','m',1,2],
 ['a','B','m',1,2]]

I would need an input like this for my next process in the pipeline.

Answer 1

The first thing I should mention is that the first channel you created is not a 2-element channel. It's a single-element channel containing

[[a, a, a, a], [B, B, B, B], [m, m, m, m], 1, 2]

This is easy to verify. Just .view() your channel and you'll see it's a single-element channel as it has a single emission.

Anyway, if you want to convert that original channel of yours to the version you showed at the end you can use the transpose operator:

tuple_ch
  .transpose()
  .toList()
  .view()

The output:

[[a, B, m, 1, 2],
 [a, B, m, 1, 2],
 [a, B, m, 1, 2],
 [a, B, m, 1, 2]]