Merge function usage with dynamic list

I guess, this is you are looking for - 

a!localVariables(
  local!a: {
    { a: 1, b: { 1, 2, 3 } },
    { a: 2, b: { "asdf", 5, 6 } },
    { a: 1, b: { 7, 8 } }
  },
  a!forEach(
    items: local!a,
    expression: fv!item.b
  )
)

Hi Tushar,

Thank you for your response. However,

I am looking for the output {{1, "asdf", 7}, {2, 5, 8}, {3, 6, null}} and not the result of foreach

In that case, this will work for you - 

a!localVariables(
  local!a: {
    { a: 1, b: { 1, 2, 3 } },
    { a: 2, b: { "asdf", 5, 6 } },
    { a: 1, b: { 7, 8 } }
  },
  a!forEach(
    items: enumerate(count(local!a.b)) + 1,
    expression: a!localVariables(
      local!index: fv!item,
      a!forEach(
        items: local!a.b,
        expression: if(
          local!index > count(fv!item),
          "",
          fv!item[local!index]
        )
      )
    )
  )
)

In that case, this will work for you - 

a!localVariables(
  local!a: {
    { a: 1, b: { 1, 2, 3 } },
    { a: 2, b: { "asdf", 5, 6 } },
    { a: 1, b: { 7, 8 } }
  },
  a!forEach(
    items: enumerate(count(local!a.b)) + 1,
    expression: a!localVariables(
      local!index: fv!item,
      a!forEach(
        items: local!a.b,
        expression: if(
          local!index > count(fv!item),
          "",
          fv!item[local!index]
        )
      )
    )
  )
)

Yeah this looks like a good outcome! For what it's worth, since a!forEach() came out, I have entirely stopped using the merge() function. You can generally achieve anything you needed to from merge() with a!forEach(), and a!forEach() is much easier to debug or set up complex logic.

A small optimization

a!localVariables(
  local!a: {
    { a: 1, b: { 1, 2, 3 } },
    { a: 2, b: { "asdf", 5, 6 } },
    { a: 1, b: { 7, 8 } }
  },
  a!forEach(
    items: enumerate(count(local!a)),
    expression: a!localVariables(
      local!index: fv!index,
      a!forEach(
        items: local!a.b,
        expression: index(fv!item, local!index, "")
      )
    )
  )
)

I guess, there is always some space for optimization.