erl_pp

1996 2007 Ericsson AB, All Rights Reserved The contents of this file are subject to the Erlang Public License, Version 1.1, (the "License"); you may not use this file except in compliance with the License. You should have received a copy of the Erlang Public License along with this software. If not, it can be retrieved online at http://www.erlang.org/. Software distributed under the License is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License for the specific language governing rights and limitations under the License. The Initial Developer of the Original Code is Ericsson AB. erl_pp Robert Virding Bjarne Däcker 1 Bjarne Däcker 97-01-24 B erl_pp.sgml

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 Pretty print a form 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 Pretty print an attribute 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 Pretty print a function 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 Pretty print a guard 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 Pretty print Expressions 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 Pretty print one Expression 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.