lfe_io(3)                                                            lfe_io(3)



NAME
       lfe_io ‐ Lisp Flavoured Erlang (LFE) io functions

SYNOPSIS
       This  module  provides  a standard set of io functions for LFE.  In the
       following description, many functions have an optional parameter  IoDe‐
       vice.   If  included, it must be the pid of a process which handles the
       IO protocols such as the IoDevice returned by file:open/2.

       Two functions in this module are used to generate aesthetically attrac‐
       tive  representations  of abstract forms, which are suitable for print‐
       ing.  These functions return (possibly deep) lists  of  characters  and
       generate an error if the form is wrong.

DATA TYPES
       chars() = [char() | chars()]

       filesexpr() = {Sexpr,Line}

       This  is  the format returned by lfe_io:parse_file/1 and is used by the
       compiler to give better error information.

EXPORTS
       get_line([[IoDevice,] Prompt]) ‐> Data | {error,ErrorInfo} | eof

       Reads a line from the standard  input  (IoDevice),  prompting  it  with
       prompt  (Prompt).   Note  that  this  call guarantees that the input is
       saved in the input hisotry.

       read([[IoDevice,] Prompt]) ‐> {ok,Sexpr} | {error,ErrorInfo} | eof

       Read an s‐expr  from  the  standard  input  (IoDevice)  with  a  prompt
       (Prompt).  Note that this is not line‐oriented in that it stops as soon
       as it has consumed enough characters.

       read_line([[IoDevice,] Prompt]) ‐> {ok,Sexpr} | {error,ErrorInfo} | eof

       Read  an  s‐expr  from  the  standard  input  (IoDevice)  with a prompt
       (Prompt).  Note that this is line‐oriented in that it reads whole lines
       discarding left‐over characters in the last line.

       read_string(String) ‐> {ok,Sexpr} | {error,ErrorInfo}

       Read an s‐expr from String.  Note that this only reads from String dis‐
       carding left‐over characters at the end of the string.

       print([IoDevice,] Sexpr) ‐> ok

       Print the s‐expr Sexpr to the standard output (IoDevice).

       print1(Sexpr) ‐> DeepCharList

       Return the list of characters which represent the s‐expr Sexpr.

       prettyprint([IoDevice,] Sexpr) ‐> ok

       Pretty print the s‐expr Sexpr to the standard output (IoDevice).

       prettyprint1(Sexpr) ‐> DeepCharList

       prettyprint1(Sexpr, Depth) ‐> DeepCharList

       prettyprint1(Sexpr, Depth, Indentation) ‐> DeepCharList

       prettyprint1(Sexpr, Depth, Indentation, LineLength) ‐> DeepCharList

       Return the list of characters which represents the prettyprinted s‐expr
       Sexpr.  Default values for Depth is 30, Indentation is 0 and LineLength
       is 80.

       format([IoDevice,] Format, Args) ‐> ok

       fwrite([IoDevice,] Format, Args) ‐> ok

       format1(Format, Args) ‐> DeepCharList

       fwrite1(Format, Args) ‐> DeepCharList

       Print formatted output.  The following commands are valid in the format
       string:

       · ~w, ~W ‐ print LFE terms

       · ~p, ~P ‐ prettyprint LFE terms

       · ~s ‐ print a string

       · ~e, ~f, ~g ‐ print floats

       · ~b, ~B ‐ based integers

       · ~x, ~X ‐ based integers with a prefix

       · ~+, ~# ‐ based integers in vanilla erlang format

       · ~c, ~n, ~i

       Currently  they behave as for vanilla erlang except that ~w, ~W, ~p, ~P
       print the terms as LFE sexprs.

       read_file(FileName) ‐> {ok,[Sexpr]} | {error,ErrorInfo}

       Read the file Filename returning a list of s‐exprs (as it should be).

       parse_file(FileName) ‐> {ok,[FileSexpr]} | {error,ErrorInfo}

       where

              FileSexpr = filesexpr()

       Read the file Filename returning a list of pairs containing s‐expr  and
       line number of the start of the s‐expr.

       scan_sexpr(Cont, Chars [,Line]) ‐> {done,Ret,RestChars}|{more,Cont1}

       This is a re‐entrant call which scans tokens from the input and returns
       a parsed sepxr.  If there are enough characters to parse a sexpr or  it
       detects  and  error  then  it  returns  {done,...} otherwise it returns
       {more,Cont} where Cont is used in the next call to scan_sexpr with more
       characters  to  try and parse a sexpr.  This is continued until a sexpr
       has been parsed.  Cont is initially [].

       It is not designed to be called directly by  an  application  but  used
       through  the i/o system where it can typically be called in an applica‐
       tion by:

       io:request(In, {get_until,unicode,Prompt,Module,scan_sexpr,[Line]})

ERROR INFORMATION
       The ErrorInfo mentioned above is the standard ErrorInfo structure which
       is returned from all IO modules.  It has the following format:

       {ErrorLine,Module,ErrorDescriptor}

       A string describing the error is obtained with the following call:

              apply(Module, format_error, ErrorDescriptor)

AUTHORS
       Robert Virding.



                                   2008‐2019                         lfe_io(3)
