erl_pp(3erl)						     Erlang Module Definition						      erl_pp(3erl)

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 print-
       ing. 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.

EXPORTS

       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).

UNKNOWN EXPRESSION HOOKS

       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:

	 Function(Expr,
		  CurrentIndentation,
		  CurrentPrecedence,
		  HookFunction)

	 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.

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 1.17.3						      erl_pp(3erl)