erl_pp - The Erlang Pretty Printer

The functions in this module are used to generate aesthetically attractive representations of abstract forms, which are suitable for printing. All functions return (possibly deep) lists of characters and generate an error if the form is wrong.

All functions can have an optional argument which specifies a hook that is called if an attempt is made to print an unknown form.

form(Form) -> DeepCharList

form(Form, HookFunction) -> DeepCharList

Types

Form = term()

HookFunction = see separate description below.

DeepCharList = [char()|DeepCharList]

Pretty prints a Form which is an abstract form of a type which is returned by erl_parse:parse_form.

attribute(Attribute) -> DeepCharList

attribute(Attribute, HookFunction) -> DeepCharList

Types

Attribute = term()

HookFunction = see separate description below.

DeepCharList = [char()|DeepCharList]

The same as form, but only for the attribute Attribute.

function(Function) -> DeepCharList

function(Function, HookFunction) -> DeepCharList

Types

Function = term()

HookFunction = see separate description below.

DeepCharList = [char()|DeepCharList]

The same as form, but only for the function Function.

guard(Guard) -> DeepCharList

guard(Guard, HookFunction) -> DeepCharList

Types

Form = term()

HookFunction = see separate description below.

DeepCharList = [char()|DeepCharList]

The same as form, but only for the guard test Guard.

exprs(Expressions) -> DeepCharList

exprs(Expressions, HookFunction) -> DeepCharList

exprs(Expressions, Indent, HookFunction) -> DeepCharList

Types

Expressions = term()

HookFunction = see separate description below.

Indent = integer()

DeepCharList = [char()|DeepCharList]

The same as form, but only for the sequence of expressions in Expressions.

expr(Expression) -> DeepCharList

expr(Expression, HookFunction) -> DeepCharList

expr(Expression, Indent, HookFunction) -> DeepCharList

expr(Expression, Indent, Precedence, HookFunction) ->-> DeepCharList

Types

Expression = term()

HookFunction = see separate description below.

Indent = integer()

Precedence =

DeepCharList = [char()|DeepCharList]

This function prints one expression. It is useful for implementing hooks (see below).

The optional argument HookFunction, shown in the functions described above, defines a function which is called when an unknown form occurs where there should be a valid expression. It can have the following formats:

Function: The hook function is called by:

none: There is no hook function

Function(Expr, 
         CurrentIndentation,
         CurrentPrecedence,
         HookFunction)

The called hook function should return a (possibly deep) list of characters. expr/4 is useful in a hook.

If CurrentIndentation is negative, there will be no line breaks and only a space is used as a separator.

It should be possible to have hook functions for unknown forms at places other than expressions.

io(3), erl_parse(3), erl_eval(3)

Robert Virding - support@erlang.ericsson.se