erl_prettypr(3)



erl_prettypr(3erl)         Erlang Module Definition         erl_prettypr(3erl)

NAME
       erl_prettypr - Pretty printing of abstract Erlang syntax trees.

DESCRIPTION
       Pretty printing of abstract Erlang syntax trees.

       This  module is a front end to the pretty-printing library module pret-
       typr, for text formatting of abstract syntax trees defined by the  mod-
       ule erl_syntax.

DATA TYPES
         context():

           A  representation of the current context of the pretty-printer. Can
           be accessed in hook functions.

         hook() = (syntaxTree(), context(),  Continuation)  ->  prettypr:docu-
         ment():

           * Continuation = (syntaxTree(), context()) -> prettypr:document()

           A call-back function for user-controlled formatting. See format/2.

         syntaxTree() = erl_syntax:syntaxTree():

           An abstract syntax tree. See the erl_syntax module for details.

EXPORTS
       best(Tree::syntaxTree()) -> empty | prettypr:document()

              Equivalent to best(Tree, []).

       best(Tree::syntaxTree(),  Options::[term()])  -> empty | prettypr:docu-
       ment()

              Creates a fixed "best" abstract layout for a syntax  tree.  This
              is similar to the layout/2 function, except that here, the final
              layout has been selected with respect to the given options.  The
              atom  empty is returned if no such layout could be produced. For
              information on the options, see the format/2 function.

              See also: best/1, format/2, layout/2, prettypr:best/3.

       format(Tree::syntaxTree()) -> string()

              Equivalent to format(Tree, []).

       format(Tree::syntaxTree(), Options::[term()]) -> string()

              Prettyprint-formats an abstract Erlang syntax tree as text.  For
              example,  if  you  have a .beam file that has been compiled with
              debug_info, the following should print the source code  for  the
              module (as it looks in the debug info representation):

                   {ok,{_,[{abstract_code,{_,AC}}]}} =
                           beam_lib:chunks("myfile.beam",[abstract_code]),
                   io:put_chars(erl_prettypr:format(erl_syntax:form_list(AC)))

              Available options:

                {hook, none | hook()}:
                  Unless  the  value is none, the given function is called for
                  each node whose list of annotations is not empty; see  below
                  for details. The default value is none.

                {paper, integer()}:
                  Specifies  the preferred maximum number of characters on any
                  line, including indentation. The default value is 80.

                {ribbon, integer()}:
                  Specifies the preferred maximum number of characters on  any
                  line, not counting indentation. The default value is 65.

                {user, term()}:
                  User-specific  data  for  use in hook functions. The default
                  value is undefined.

                {encoding, epp:source_encoding()}:
                  Specifies the encoding of the generated file.

              A hook function (cf. the hook() type) is passed the current syn-
              tax  tree node, the context, and a continuation. The context can
              be examined and manipulated by functions such as get_ctxt_user/1
              and  set_ctxt_user/2.  The  hook  must  return a "document" data
              structure (see layout/2 and best/2); this may be constructed  in
              part  or in whole by applying the continuation function. For ex-
              ample, the following is a trivial hook:

                    fun (Node, Ctxt, Cont) -> Cont(Node, Ctxt) end

              which yields the same result as if no hook was given.  The  fol-
              lowing, however:

                    fun (Node, Ctxt, Cont) ->
                        Doc = Cont(Node, Ctxt),
                        prettypr:beside(prettypr:text("<b>"),
                                        prettypr:beside(Doc,
                                                        prettypr:text("</b>")))
                    end

              will place the text of any annotated node (regardless of the an-
              notation data) between HTML "boldface begin" and "boldface  end"
              tags.

              See  also:  erl_syntax,  best/2, format/1, get_ctxt_user/1, lay-
              out/2, set_ctxt_user/2.

       get_ctxt_hook(Ctxt::context()) -> hook()

              Returns the hook function field of the prettyprinter context.

              See also: set_ctxt_hook/2.

       get_ctxt_linewidth(Ctxt::context()) -> integer()

              Returns the line widh field of the prettyprinter context.

              See also: set_ctxt_linewidth/2.

       get_ctxt_paperwidth(Ctxt::context()) -> integer()

              Returns the paper widh field of the prettyprinter context.

              See also: set_ctxt_paperwidth/2.

       get_ctxt_precedence(Ctxt::context()) -> integer()

              Returns the operator precedence field of the prettyprinter  con-
              text.

              See also: set_ctxt_precedence/2.

       get_ctxt_user(Ctxt::context()) -> term()

              Returns the user data field of the prettyprinter context.

              See also: set_ctxt_user/2.

       layout(Tree::syntaxTree()) -> prettypr:document()

              Equivalent to layout(Tree, []).

       layout(Tree::syntaxTree(), Options::[term()]) -> prettypr:document()

              Creates  an  abstract document layout for a syntax tree. The re-
              sult represents a set of possible layouts (cf. module prettypr).
              For  information  on  the  options, see format/2; note, however,
              that the paper and ribbon options are ignored by this function.

              This function provides  a  low-level  interface  to  the  pretty
              printer,  returning  a  flexible representation of possible lay-
              outs, independent of the paper width eventually to be  used  for
              formatting.  This  can  be  included as part of another document
              and/or further processed directly by the functions in the  pret-
              typr  module,  or  used in a hook function (see format/2 for de-
              tails).

              See also: prettypr, format/2, layout/1.

       set_ctxt_hook(Ctxt::context(), Hook::hook()) -> context()

              Updates the hook function field of the prettyprinter context.

              See also: get_ctxt_hook/1.

       set_ctxt_linewidth(Ctxt::context(), W::integer()) -> context()

              Updates the line widh field of the prettyprinter context.

              Note: changing this value (and passing the resulting context  to
              a  continuation function) does not affect the normal formatting,
              but may affect user-defined behaviour in hook functions.

              See also: get_ctxt_linewidth/1.

       set_ctxt_paperwidth(Ctxt::context(), W::integer()) -> context()

              Updates the paper widh field of the prettyprinter context.

              Note: changing this value (and passing the resulting context  to
              a  continuation function) does not affect the normal formatting,
              but may affect user-defined behaviour in hook functions.

              See also: get_ctxt_paperwidth/1.

       set_ctxt_precedence(Ctxt::context(), Prec::integer()) -> context()

              Updates the operator precedence field of the prettyprinter  con-
              text. See the erl_parse(3erl) module for operator precedences.

              See also: erl_parse(3erl), get_ctxt_precedence/1.

       set_ctxt_user(Ctxt::context(), X::term()) -> context()

              Updates the user data field of the prettyprinter context.

              See also: get_ctxt_user/1.

AUTHORS
       Richard Carlsson <carlsson.richard@gmail.com>

                               syntax_tools 2.3             erl_prettypr(3erl)

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