Get index position as value while doing `do list`

[TobiasNx]

For a hbz project we need the option to state the position of an value within an array, e.g. while doing do list.

There are three ways I can think of how to manage this:

a) a function index_position that adds/creates an element with the position while iterating over an list:

input:

a:
    - dog
    - cat
    - bird

set_array("animals[]")
do list("a","var":"$i")
    copy_field("$i","animals[].$append.name")
    index_position("$i","animals[].$last.pos")
end
retain("animals[]")

animals:
    - name: dog
      pos: 1
    - name: cat
      pos: 2
    - name: bird
      pos: 3

2) Something with using a function that is requested in #348. To get the path as value and delete everything but the trailing digits:

input:

a:
    - dog
    - cat
    - bird

set_array("animals[]")
do list("a","var":"$i")
    copy_field("$i","animals[].$append.name")
    path_as_value("$i","animals[].$last.pos")
end

replace_all("animals[].*.pos","^.*(\\d*)$","$1")
retain("animals[]")

animals:
    - name: dog
      pos: 1
    - name: cat
      pos: 2
    - name: bird
      pos: 3

3) Providing a counter, that adds a value everytime a path is requested:

input:

a:
    - dog
    - cat
    - bird

set_array("animals[]")
do list("a","var":"$i")
    copy_field("$i","animals[].$append.name")
    counter("$i","animals[].$last.pos")
end

retain("animals[]")

animals:
    - name: dog
      pos: 1
    - name: cat
      pos: 2
    - name: bird
      pos: 3

[TobiasNx]

It could also be solved in a more complex way with a math function which is requested in #350

[blackwinter]

For a hbz project we need the option to state the position of an value within an array, e.g. while doing do list.

Can you clarify what the actual use case is? Why do you need the position?

[TobiasNx]

Transforming data to mets and creating a structural reference within the metadata based on the position within the transformation. The usecase is to replace the position() function of an xslt, or number() function, as stated in this discussion:

https://stackoverflow.com/questions/4449810/using-position-function-in-xslt

[TobiasNx]

i thought I have a workaround, but this not to be working:

would be a complex solution for this:

set_array("animals[]")
set_array("animals_index")
do list(path:"a[]","var":"$i")
    copy_field("$i","animals[].$append.name")
    copy_field("$i","animals_index.$append")
    copy_field("animals_index","animals[].$last.pos")
end

count("animals[].*.pos")
retain("animals[]")

This results in:

{
  "animals" : [ {
    "name" : "dog",
    "pos" : "6"
  }, {
    "name" : "cat",
    "pos" : "6"
  }, {
    "name" : "bird",
    "pos" : "6"
  } ]
}

PS: And this variant:

set_array("animals[]")
set_array("animals_index")
do list(path:"a[]","var":"$i")
    copy_field("$i","animals[].$append.name")
    copy_field("$i","animals_index.$append")
    copy_field("animals_index","animals[].$append.pos")
end

do list(path:"animals[]","var":"$i")
    count("$i.pos")
end

retain("animals[]")

Results in

{
  "animals" : [ {
    "name" : "dog",
    "pos" : "dog"
  }, {
    "name" : "cat",
    "pos" : "2"
  }, {
    "name" : "bird",
    "pos" : "3"
  } ]
}

So almost. This seems to be connected to #239

[blackwinter]

Clever idea ;) Yes, you have to do it in each iteration instead of once at the end:

set_array("animals[]")
set_array("animals_index")

do list(path: "a[]", "var": "$i")
  copy_field("$i", "animals[].$append.name")

  # keep track of items (globally)
  copy_field("$i", "animals_index.$append")

  # determine current count (locally)
  set_array("animals[].$last.pos")
  copy_field("animals_index", "animals[].$last.pos.$append")
  count("animals[].$last.pos")
end

retain("animals[]")