Conditional structures: Difference between revisions

=={{header|jq}}==

jq's main conditional construct is:<lang jq>if cond then f else g end</lang>where cond, f, and g, are filters, and where cond may evaluate to anything at all, it being understood that:

# all JSON values are truthy except for false and null;

# if cond evaluates to nothing (i.e., produces an empty stream), then the entire if-then-else-end expression also produces an empty stream.

For example:<lang jq>

if empty then 2 else 3 end # produces no value

if 1 then 2 else 3 end # produces 2

if [false, false] then 2 else 3 end # produces 2

if (true, true) then 2 else 3 end # produces a stream: 2, 2

</lang>Notice that if cond produces a nonempty stream, then the entire expression will typically do the same. Since f and g also can produce streams, this lends itself to interesting Cartesian-product possibilities.

Since jq's <tt>and</tt> and <tt>or</tt> are short-circuiting, they can also be used for branching.