Return true if a given source is currently setting.

Arguments:

Source source

The source of interest.

Example 1:

The following example shows one way to wait for a source to rise, and stop waiting if the source has recently set.

  until $visible(jupiter) | $setting(jupiter)
  if($visible(jupiter)) {
    ...
  }

Context:

A source is considered to be setting if its elevation is decreasing.