Comprehensions

Comprehensions in general

Comprehensions are a concise syntax to define a list of elements, as an alternative to listing the elements or using functions to construct them.

Comprehensions combine the functionality of map, filter and other functions.

Comprehensions can be used to construct lists or objects.

The simplest form of a list comprehension is demonstrated by this example:

[each .author.name in .articles]

Which is equivalent to the following filter:

.articles | map $ => .author.name

It is possible to add a condition to filter the input in the comprehension:

[each .author.name in .articles if .author.city == "London"]

Which is equivalent to the following filter:

.articles | filter $ => .author.city == "London" | map $ => .author.name

Finally, for the sake of convenience the list comprehension can be extended by a custom filter:

[each .author.name in .articles if .author.city == "London" sortBy $ => .author.age]

Which is equivalent to the following filter:

.articles | sortBy $ => .author.age | filter $ => .author.city == "London" | map $ => .author.name

Object comprehensions work in exactly the same way, except that they are wrapped in curly braces:

{ each (.author.name): (2018 - .author.age) in .articles }