Introduce constants in base functions

Feature requests
1

Use case or problem

Introduce a constant inside a function scope (for reusing/naming a result).

If I am working with a more complex formula in bases, I have only one easy way to simplify the process and that is to break it down into multiple formulae, and use the output of one in another. E.g. file.backlinks.contains(formula.other_formula)

However, this is not directly possible when inside a map. If I am mapping e.g. over the backlinks of a file, and for each of those backlinks computing something further, it might be nice to be able to assign the further computation to a name.

It is possible in to refactor as a series of maps and filters (also see the workaround below) but this is what I normally end up with

file.backlinks.filter(
    value.asFile().backlinks.filter(another_function_etc).length > 0 
    /* Exact same function of the backlink written below */
    && value.asFile().backlinks.filter(another_function_etc).length < 10
)

which could be

file.backlinks.filter(
    /*result defined somewhere here?*/
    result > 0 && result < 10 
)

Proposed solution

A couple of ideas:

1. Naming variables

Taking inspiration from the ~somewhat similar pipelines in jq, we could write something like this

file.backlinks.filter(
    with value.asFile().backlinks.filter(another_function_etc).length as result;
    result > 0 && result < 10 
)

which could be extended for multiple definitions like e.g.:

file.backlinks.filter(
    with <function_1_of_value> as result, <function_2_of_value> as result_2;
    result > 0 && result < 10 
)

let … in is another syntax that is often used.

2. Defining objects

Make it possible to create objects, which could be used to store intermediate results, e.g.:

file.backlinks
    .map(
        /* Make an intermediate object, storing the result alongside the backlink */
        {"link": value, "func_result": value.asFile.backlinks...}
    ).filter(
                value["result"] > 0 && value["result"] < 10 
    ).map(value["link"])

Current workaround - using lists

While I don’t believe you can create objects, you can create lists, and store intermediate values in the list, e.g:

file.backlinks
    .map(
        /* Make a list, storing the result alongside the backlink */
        [value, value.asFile.backlinks...]
    ).filter(
                value[1] > 0 && value[1] < 10 
    ).map(value[0])