Possible approaches to iteration

[tom.r...@gmail.com]

I would like to understand semantics of `with_items` in ansible and compare this approach to `map` for example. 

For example, let consider:  

`{{ ["1","2", "3"]  | map('regex_replace', '^(.*)$', \1'some tail')  tail }}`

How to reach the same effect using `with_items` ? 

And in general how does it work ? Where is the body of this loop ?

For example (got from some stack overflow thread):

    ---

    - hosts: localhost

      tasks:

      - name: set fact 1

        set_fact: foo="[ 'zero' ]"

    

      - name: set fact 2

        set_fact: foo="{{ foo }} + [ 'one' ]"

    

      - name: set fact 3

        set_fact: foo="{{ foo }} + [ 'two', 'three' ]"

    

      - name: set fact 4

        set_fact: foo="{{ foo }} + [ '{{ item }}' ]"

        with_items:

          - four

          - five

          - six

    

      - debug: var=foo

To sum up, the question is about which approach is better (`map` vs `with_items`) and possible details of working (e.g. where  is body of this loop) 

Each detail of working ansible is welcome!

[Brian Coca]

In the case of 'set_fact' you should not see much difference, but in
most other cases map will always be faster, with_<lookup> executes the
task once per item, except when squashing, but that is magic reserved
to only a few plugins.

FYI the 'item's part is equivalent of loop: '{{ [ "four", "five",
"six"] | flatten(depth=1) }}', a closer representation to map would be
with_list.



--
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Brian Coca