Undefined values: Difference between revisions

=={{header|jq}}==

In jq as in JSON, null can usually be used to represent an undefined or unspecified value. However, in jq, 1/0 does not yield null:

<lang sh>$ jq -n '1/0 == null'

false</lang>

It should also be noted that in jq, null can combine with other values to form non-null values. Specifically, for any JSON entity, e,

both null + e and e + null evaluate to e. This is often convenient as it avoids having to handle edge cases specially.

For example, suppose it is agreed that the "sum" of the elements of an empty array should be null. Then one can simply write:

<lang jq>def sum: reduce .[] as $x (null; . + $x);</lang>