NAME

       erl_pp - The Erlang Pretty Printer

DESCRIPTION

       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.

DATA TYPES

       hook_function() =
           none |
           fun((Expr :: erl_parse:abstract_expr(),
                CurrentIndentation :: integer(),
                CurrentPrecedence :: integer() >= 0,
                Options :: options()) ->
                   io_lib:chars())

              The optional argument HookFunction, shown in the functions described  below,  defines  a  function
              which is called when an unknown form occurs where there should be a valid expression.

              If HookFunction is equal to none there is no hook function.

              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.

       option() =
           {hook, hook_function()} | {encoding, latin1 | unicode | utf8}

       options() = hook_function() | [option()]

EXPORTS

       form(Form) -> io_lib:chars()

       form(Form, Options) -> io_lib:chars()

              Types:

                 Form = erl_parse:abstract_form()
                 Options = options()

              Pretty  prints  a  Form  which  is  an  abstract  form  of   a   type   which   is   returned   by
              erl_parse:parse_form/1.

       attribute(Attribute) -> io_lib:chars()

       attribute(Attribute, Options) -> io_lib:chars()

              Types:

                 Attribute = erl_parse:abstract_form()
                 Options = options()

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

       function(Function) -> io_lib:chars()

       function(Function, Options) -> io_lib:chars()

              Types:

                 Function = erl_parse:abstract_form()
                 Options = options()

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

       guard(Guard) -> io_lib:chars()

       guard(Guard, Options) -> io_lib:chars()

              Types:

                 Guard = [erl_parse:abstract_expr()]
                 Options = options()

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

       exprs(Expressions) -> io_lib:chars()

       exprs(Expressions, Options) -> io_lib:chars()

       exprs(Expressions, Indent, Options) -> io_lib:chars()

              Types:

                 Expressions = [erl_parse:abstract_expr()]
                 Indent = integer()
                 Options = options()

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

       expr(Expression) -> io_lib:chars()

       expr(Expression, Options) -> io_lib:chars()

       expr(Expression, Indent, Options) -> io_lib:chars()

       expr(Expression, Indent, Precedence, Options) -> io_lib:chars()

              Types:

                 Expression = erl_parse:abstract_expr()
                 Indent = integer()
                 Precedence = integer() >= 0
                 Options = options()

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

BUGS

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

SEE ALSO

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

Ericsson AB                                        stdlib 2.8                                       erl_pp(3erl)