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.
Functions
form(Form) -> DeepCharList
form(Form, HookFunction) -> DeepCharList
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
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
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
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
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
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.