Change the indentation of lists

The default options map for lists is as follows:

 :list {:constant-pair-min 4,
        :constant-pair? true,
        :hang-avoid 0.5,
        :hang-diff 1,
        :hang-expand 2.0,
        :hang-size 100,
        :hang? true,
        :indent 2,
        :indent-arg nil,
        :indent-only-style :input-hang,
        :indent-only? false,
        :pair-hang? true,
        :replacement-string nil,
        :respect-nl? false},

Indentation for lists is primarily configured by :indent, though :indent-arg will come into play if it is non-nil.

What is a hang and how does it differ from a flow?

zprint has a name for these two different approaches to formatting:

• Hang

(this is
      a
      hang)

• Flow

(this
  is
  a
  flow)

When does zprint do a hang or a flow?

There are a number of complex heuristics about when zprint will do a hang or a flow, depending in many cases on how many lines it will take (less is better), and how it will "look". To simplify this situation, the basic rules are:

zprint will hang when:

• The entire list will not fit in the remaining space on the current line
• The first element of a list could be a function name
• The hang approach will not take more lines than the flow approach
• Some other complex calculations on how it will "look"

Clearly, when zprint is doing a hang, the configured :indent is meaningless, since the indent for the subsequent lines is based on the size of the first element of the list.

When does zprint use :indent?

zprint will use the :indent for a list when it is doing a flow, which is when:

• The entire list will not fit in the remaining space on the current line
• The first element of a list could be a function name
• A flow is considered "better" than a hang

In this case, zprint will place a number of spaces controlled by :indent in front of the second and subsequent elements of the list.

Note that if zprint doesn't think that the first element can be a function name (for example, it is a number), then zprint will not use :indent for subsequent elements, it will use a single space. For example:

(555
 aaaa
 bbbb
 cccc)

Different indents for body functions and argument functions?

There is a full discussion of this in community standards.

How to change indents for lists?

You can place an options map which contains {:list {:indent n}} or {:list {:indent-arg n}} anywhere an options map is accepted.