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Q&A Replace leaf arrays with joined strings in a nested structure in jq

As the walk documentation describes: When an array is encountered, f is first applied to its elements and then to the array itself In other words, walk is bottom-up. So when you apply your fi...

posted 8mo ago by r~~‭  ·  edited 8mo ago by r~~‭

Answer
#5: Post edited by user avatar r~~‭ · 2023-09-09T08:18:23Z (8 months ago)
revert meddling
  • Explanation
  • -
  • As the [`walk` documentation](https://jqlang.github.io/jq/manual/#walk) describes:
  • > When an array is encountered, f is first applied to its elements and then to the array itself
  • In other words, `walk` is bottom-up. So when you apply your filter to your nested-array input, first you're flattening the innermost arrays into strings. Then the arrays at the next level out are arrays of strings, and they get flattened; and so on up the structure. It's not doing anything to your objects because you wrote the filter to only alter arrays.
  • Solution 1
  • -
  • You can see the definition of `walk` in the [jq repository](https://github.com/jqlang/jq/blob/df95871dd7415627bda6d70ce0569d0a4fbc22c6/src/builtin.jq#L248C1-L256C5); from this it is easy to make a top-down variation that will do what you want, by simply moving the `f` from the right side of the pipe to the left.
  • ```jq
  • def walktd(f):
  • def w:
  • f |
  • if type == "object"
  • then map_values(w)
  • elif type == "array" then map(w)
  • else .
  • end;
  • w;
  • walktd(if type == "array" and
  • all(type != "array" and type != "object")
  • then join("") else . end)
  • ```
  • Solution 2
  • -
  • Alternatively, if you don't want to define your own function, you *can* do this with `walk` but you need to do a bunch of wrapping and unwrapping, in order to distinguish between a string that was produced by collapsing an array and a string that appeared in the original input:
  • ```jq
  • walk(if type == "object"
  • then {
  • value: map_values(.value),
  • atom: false
  • }
  • elif type == "array"
  • then {
  • value: (if all(.atom) then map(.value) | join("") else map(.value) end),
  • atom: false
  • }
  • else {
  • value: .,
  • atom: true
  • }
  • end).value
  • ```
  • As the [`walk` documentation](https://jqlang.github.io/jq/manual/#walk) describes:
  • > When an array is encountered, f is first applied to its elements and then to the array itself
  • In other words, `walk` is bottom-up. So when you apply your filter to your nested-array input, first you're flattening the innermost arrays into strings. Then the arrays at the next level out are arrays of strings, and they get flattened; and so on up the structure. It's not doing anything to your objects because you wrote the filter to only alter arrays.
  • You can see the definition of `walk` in the `jq` repository [here](https://github.com/jqlang/jq/blob/df95871dd7415627bda6d70ce0569d0a4fbc22c6/src/builtin.jq#L248C1-L256C5); from this it is easy to make a top-down variation that will do what you want, by simply moving the `f` from the right side of the pipe to the left.
  • ```jq
  • def walktd(f):
  • def w:
  • f |
  • if type == \"object\"
  • then map_values(w)
  • elif type == \"array\" then map(w)
  • else .
  • end;
  • w;
  • walktd(if type == \"array\" and
  • all(type != \"array\" and type != \"object\")
  • then join(\"\") else . end)
  • ```
  • Alternatively, if you don't want to define your own function, you *can* do this with `walk` but you need to do a bunch of wrapping and unwrapping, in order to distinguish between a string that was produced by collapsing an array and a string that appeared in the original input:
  • ```jq
  • walk(if type == \"object\"
  • then {
  • value: map_values(.value),
  • atom: false
  • }
  • elif type == \"array\"
  • then {
  • value: (if all(.atom) then map(.value) | join(\"\") else map(.value) end),
  • atom: false
  • }
  • else {
  • value: .,
  • atom: true
  • }
  • end).value
  • ```
#4: Post edited by user avatar meta user‭ · 2023-09-05T06:13:40Z (8 months ago)
edit link, add headings
  • As the [`walk` documentation](https://jqlang.github.io/jq/manual/#walk) describes:
  • > When an array is encountered, f is first applied to its elements and then to the array itself
  • In other words, `walk` is bottom-up. So when you apply your filter to your nested-array input, first you're flattening the innermost arrays into strings. Then the arrays at the next level out are arrays of strings, and they get flattened; and so on up the structure. It's not doing anything to your objects because you wrote the filter to only alter arrays.
  • You can see the definition of `walk` in the `jq` repository [here](https://github.com/jqlang/jq/blob/df95871dd7415627bda6d70ce0569d0a4fbc22c6/src/builtin.jq#L248C1-L256C5); from this it is easy to make a top-down variation that will do what you want, by simply moving the `f` from the right side of the pipe to the left.
  • ```jq
  • def walktd(f):
  • def w:
  • f |
  • if type == "object"
  • then map_values(w)
  • elif type == "array" then map(w)
  • else .
  • end;
  • w;
  • walktd(if type == "array" and
  • all(type != "array" and type != "object")
  • then join("") else . end)
  • ```
  • Alternatively, if you don't want to define your own function, you *can* do this with `walk` but you need to do a bunch of wrapping and unwrapping, in order to distinguish between a string that was produced by collapsing an array and a string that appeared in the original input:
  • ```jq
  • walk(if type == "object"
  • then {
  • value: map_values(.value),
  • atom: false
  • }
  • elif type == "array"
  • then {
  • value: (if all(.atom) then map(.value) | join("") else map(.value) end),
  • atom: false
  • }
  • else {
  • value: .,
  • atom: true
  • }
  • end).value
  • ```
  • Explanation
  • -
  • As the [`walk` documentation](https://jqlang.github.io/jq/manual/#walk) describes:
  • > When an array is encountered, f is first applied to its elements and then to the array itself
  • In other words, `walk` is bottom-up. So when you apply your filter to your nested-array input, first you're flattening the innermost arrays into strings. Then the arrays at the next level out are arrays of strings, and they get flattened; and so on up the structure. It's not doing anything to your objects because you wrote the filter to only alter arrays.
  • Solution 1
  • -
  • You can see the definition of `walk` in the [jq repository](https://github.com/jqlang/jq/blob/df95871dd7415627bda6d70ce0569d0a4fbc22c6/src/builtin.jq#L248C1-L256C5); from this it is easy to make a top-down variation that will do what you want, by simply moving the `f` from the right side of the pipe to the left.
  • ```jq
  • def walktd(f):
  • def w:
  • f |
  • if type == "object"
  • then map_values(w)
  • elif type == "array" then map(w)
  • else .
  • end;
  • w;
  • walktd(if type == "array" and
  • all(type != "array" and type != "object")
  • then join("") else . end)
  • ```
  • Solution 2
  • -
  • Alternatively, if you don't want to define your own function, you *can* do this with `walk` but you need to do a bunch of wrapping and unwrapping, in order to distinguish between a string that was produced by collapsing an array and a string that appeared in the original input:
  • ```jq
  • walk(if type == "object"
  • then {
  • value: map_values(.value),
  • atom: false
  • }
  • elif type == "array"
  • then {
  • value: (if all(.atom) then map(.value) | join("") else map(.value) end),
  • atom: false
  • }
  • else {
  • value: .,
  • atom: true
  • }
  • end).value
  • ```
#3: Post edited by user avatar r~~‭ · 2023-09-04T04:56:19Z (8 months ago)
  • As the [`walk` documentation](https://jqlang.github.io/jq/manual/#walk) describes:
  • > When an array is encountered, f is first applied to its elements and then to the array itself
  • In other words, `walk` is bottom-up. So when you apply your filter to your nested-array input, first you're flattening the innermost arrays into strings. Then the arrays at the next level out are arrays of strings, and they get flattened; and so on up the structure. It's not doing anything to your objects because you wrote the filter to only alter arrays.
  • You can see the definition of `walk` in the `jq` repository [here](https://github.com/jqlang/jq/blob/df95871dd7415627bda6d70ce0569d0a4fbc22c6/src/builtin.jq#L248C1-L256C5); from this it is easy to make a top-down variation that will do what you want, by simply moving the `f` from the right side of the pipe to the left.
  • ```jq
  • def walktd(f):
  • def w:
  • f |
  • if type == "object"
  • then map_values(w)
  • elif type == "array" then map(w)
  • else .
  • end;
  • w;
  • walktd(if type == "array" and
  • all(type != "array" and type != "object")
  • then join("") else . end)
  • ```
  • Alternatively, if you don't want to define your own function, you *can* do this with `walk` but you need to do a bunch of wrapping and unwrapping, in order to distinguish between a string that was produced by collapsing an array and a string that appeared in the original input:
  • ```jq
  • walk(if type == "object"
  • then {
  • value: map_values(.value),
  • atom: false
  • }
  • elif type == "array"
  • then {
  • value: (if all(.atom) then map(.value) | join("") else map(.value) end),
  • atom: false
  • }
  • else {
  • value: .,
  • atom: true
  • }
  • end).value
  • ```
  • As the [`walk` documentation](https://jqlang.github.io/jq/manual/#walk) describes:
  • > When an array is encountered, f is first applied to its elements and then to the array itself
  • In other words, `walk` is bottom-up. So when you apply your filter to your nested-array input, first you're flattening the innermost arrays into strings. Then the arrays at the next level out are arrays of strings, and they get flattened; and so on up the structure. It's not doing anything to your objects because you wrote the filter to only alter arrays.
  • You can see the definition of `walk` in the `jq` repository [here](https://github.com/jqlang/jq/blob/df95871dd7415627bda6d70ce0569d0a4fbc22c6/src/builtin.jq#L248C1-L256C5); from this it is easy to make a top-down variation that will do what you want, by simply moving the `f` from the right side of the pipe to the left.
  • ```jq
  • def walktd(f):
  • def w:
  • f |
  • if type == "object"
  • then map_values(w)
  • elif type == "array" then map(w)
  • else .
  • end;
  • w;
  • walktd(if type == "array" and
  • all(type != "array" and type != "object")
  • then join("") else . end)
  • ```
  • Alternatively, if you don't want to define your own function, you *can* do this with `walk` but you need to do a bunch of wrapping and unwrapping, in order to distinguish between a string that was produced by collapsing an array and a string that appeared in the original input:
  • ```jq
  • walk(if type == "object"
  • then {
  • value: map_values(.value),
  • atom: false
  • }
  • elif type == "array"
  • then {
  • value: (if all(.atom) then map(.value) | join("") else map(.value) end),
  • atom: false
  • }
  • else {
  • value: .,
  • atom: true
  • }
  • end).value
  • ```
#2: Post edited by user avatar r~~‭ · 2023-09-04T04:52:51Z (8 months ago)
  • As the [`walk` documentation](https://jqlang.github.io/jq/manual/#walk) describes:
  • > When an array is encountered, f is first applied to its elements and then to the array itself
  • In other words, `walk` is bottom-up. So when you apply your filter to your nested-array input, first you're flattening the innermost arrays into strings. Then the arrays at the next level out are arrays of strings, and they get flattened; and so on up the structure. It's not doing anything to your objects because you wrote the filter to only alter arrays.
  • You can see the definition of `walk` in the `jq` repository [here](https://github.com/jqlang/jq/blob/df95871dd7415627bda6d70ce0569d0a4fbc22c6/src/builtin.jq#L248C1-L256C5); from this it is easy to make a top-down variation that will do what you want, by simply moving the `f` from the right side of the pipe to the left.
  • ```jq
  • def walktd(f):
  • def w:
  • f |
  • if type == "object"
  • then map_values(w)
  • elif type == "array" then map(w)
  • else .
  • end;
  • w;
  • walktd(if type == "array" and
  • all(type != "array" and type != "object")
  • then join("") else . end)
  • ```
  • As the [`walk` documentation](https://jqlang.github.io/jq/manual/#walk) describes:
  • > When an array is encountered, f is first applied to its elements and then to the array itself
  • In other words, `walk` is bottom-up. So when you apply your filter to your nested-array input, first you're flattening the innermost arrays into strings. Then the arrays at the next level out are arrays of strings, and they get flattened; and so on up the structure. It's not doing anything to your objects because you wrote the filter to only alter arrays.
  • You can see the definition of `walk` in the `jq` repository [here](https://github.com/jqlang/jq/blob/df95871dd7415627bda6d70ce0569d0a4fbc22c6/src/builtin.jq#L248C1-L256C5); from this it is easy to make a top-down variation that will do what you want, by simply moving the `f` from the right side of the pipe to the left.
  • ```jq
  • def walktd(f):
  • def w:
  • f |
  • if type == "object"
  • then map_values(w)
  • elif type == "array" then map(w)
  • else .
  • end;
  • w;
  • walktd(if type == "array" and
  • all(type != "array" and type != "object")
  • then join("") else . end)
  • ```
  • Alternatively, if you don't want to define your own function, you *can* do this with `walk` but you need to do a bunch of wrapping and unwrapping, in order to distinguish between a string that was produced by collapsing an array and a string that appeared in the original input:
  • ```jq
  • walk(if type == "object"
  • then {
  • value: map_values(.value),
  • atom: false
  • }
  • elif type == "array"
  • then {
  • value: (if all(.atom) then map(.value) | join("") else map(.value) end),
  • atom: false
  • }
  • else {
  • value: .,
  • atom: true
  • }
  • end).value
  • ```
#1: Initial revision by user avatar r~~‭ · 2023-09-04T01:19:14Z (8 months ago)
As the [`walk` documentation](https://jqlang.github.io/jq/manual/#walk) describes:


 >  When an array is encountered, f is first applied to its elements and then to the array itself

In other words, `walk` is bottom-up. So when you apply your filter to your nested-array input, first you're flattening the innermost arrays into strings. Then the arrays at the next level out are arrays of strings, and they get flattened; and so on up the structure. It's not doing anything to your objects because you wrote the filter to only alter arrays.

You can see the definition of `walk` in the `jq` repository [here](https://github.com/jqlang/jq/blob/df95871dd7415627bda6d70ce0569d0a4fbc22c6/src/builtin.jq#L248C1-L256C5); from this it is easy to make a top-down variation that will do what you want, by simply moving the `f` from the right side of the pipe to the left.

```jq
def walktd(f):
  def w:
    f |
    if type == "object"
    then map_values(w)
    elif type == "array" then map(w)
    else .
    end;
  w;

walktd(if type == "array" and
       all(type != "array" and type != "object")
       then join("") else . end)
```